You’ve closed a deal. Now comes the hard part: making it work.
According to KPMG, 83% of M&A deals fail to boost shareholder returns. Not “underperform.” Fail. And when Bain asked practitioners why, the same percentage pointed to one thing: poor integration execution.
So should you hire a PMI consultant after an acquisition? It depends on what you’re facing—and what you can handle internally.
This is where PMI consultants come in. But what do they actually do? And do you need one?
What Does a PMI Consultant Actually Do?
PMI stands for Post-Merger Integration. A PMI consultant helps two companies become one—or at least work together without tripping over each other.
But “integration” covers a lot of ground. PMI consultants typically work across five areas:
1. Integration Strategy & Planning
Before anyone touches a system or moves an employee, someone needs to answer: what are we actually trying to achieve here?
A PMI consultant helps define: - Integration scope — What gets unified, what stays separate, what gets shut down - Synergy targets — Where’s the value coming from, and who’s accountable for delivering it - Sequencing — What happens first, second, third (and why) - Governance — Who makes decisions, how conflicts get resolved
This isn’t strategy for strategy’s sake. Research from Global PMI Partners shows deals where synergies are explicitly validated and tracked from the start have a 92% success rate—compared to baseline rates of 14-40%. The planning phase is where most of that value gets locked in or lost.
2. Operational Integration
This is the blocking and tackling: combining processes, teams, and ways of working.
- Org design — Reporting lines, role clarity, eliminating redundancies
- Process harmonisation — Aligning how the two companies do things (procurement, sales, customer service, etc.)
- Policy alignment — HR policies, expense rules, approval workflows
- Vendor consolidation — Rationalising suppliers and contracts
Operational integration is where the “people pain” lives. The acquired company did things one way. The acquirer does them another. Someone has to figure out which approach wins—and manage the transition for those whose processes didn’t.
3. Systems & Technology Integration
This is often the most visible (and expensive) part of integration:
- System consolidation — CRM, ERP, email, HR systems, operational tools
- Data migration — Moving data from legacy systems without losing history or breaking processes
- IT infrastructure — Networks, security, access controls
84% of IT integrations fail or experience significant issues. That’s not a typo. Systems integration is where many deals quietly fall apart—not in a dramatic explosion, but in a slow bleed of missed deadlines and frustrated employees.
4. Change Management & Communications
The most underrated part of integration. You can have the perfect technical plan and still fail because people don’t adopt the new way of working.
- Stakeholder management — Identifying who’s on board, who’s resistant, who’s quietly sabotaging
- Communications — Keeping everyone informed without overwhelming them
- Training — Getting people competent on new systems and processes
- Adoption monitoring — Tracking whether the changes are actually sticking
Research shows 47% of employees leave in Year 1 after an acquisition—3.6 times the normal turnover rate. Much of that exodus traces back to poor change management: people feeling unheard, unclear on their future, or simply not trained on new tools.
5. Integration Programme Management
Someone has to keep all these workstreams moving in the same direction:
- Timeline management — Tracking milestones, identifying blockers, escalating issues
- Resource coordination — Making sure the right people are working on the right things
- Risk management — Spotting problems before they derail the programme
- Reporting — Keeping the board, sponsors, and leadership informed
This role is often called the Integration Management Office (IMO) or PMI lead. Deals with a dedicated integration leader achieve their strategic goals 75% of the time—yet fewer than half of companies actually establish one.
Types of PMI Consultants
Not all PMI consultants do all five of the above. The market has specialised:
Strategy-focused firms (McKinsey, Bain, BCG) tend to work on integration strategy, synergy identification, and operating model design. Strong on planning, less hands-on during execution.
Big 4 firms (Deloitte, PwC, KPMG, EY) offer end-to-end capabilities—strategy through execution—with large teams that can handle complex, multi-geography deals.
System specialists (Salesforce partners, NetSuite consultants, Microsoft partners) focus narrowly on their platform. Deep expertise in the destination system, less in the source-side chaos.
Boutique integration firms work specifically on mid-market deals, often with more hands-on execution and lower overhead than the big firms.
The PMI consulting market is worth $8 billion and growing at 10%+ annually. Accenture, Bain, and BCG together hold about 60% market share—but there’s a long tail of specialists serving different segments.
For a deeper comparison of all your resourcing options (including in-house and hybrid approaches), see Who Should Handle Post-Merger Integration.
When You Probably Need a PMI Consultant
Not every acquisition needs external help. But some situations clearly benefit from it:
You’re integrating for the first time. If this is your first acquisition (or first significant one), you don’t have internal playbooks, experienced staff, or institutional memory to draw on. A consultant brings experience you don’t have yet.
The deal is complex. Multiple locations. Multiple systems. Multiple countries. Regulatory sensitivities. When there are many moving parts, having someone who’s seen it before reduces the risk of expensive mistakes.
The timeline is tight. PE sponsors want synergies in 12 months. The CFO needs consolidated reporting by Q3. Tight timelines don’t allow for learning on the job—experienced consultants bring speed that internal teams learning on the fly simply can’t match.
Your team is already stretched. Your IT team is keeping the lights on. Your ops team is hitting targets. Adding a major integration project doesn’t create more hours in the day—something gives. External help provides capacity without degrading other work.
Change management is going to be hard. The acquired company’s staff were promised “nothing will change.” The founder is staying on and has opinions. There’s an us-vs-them dynamic brewing. A consultant can play the “neutral third party” role that internal staff can’t.
You’re building a repeatable programme. If this is acquisition #1 of 10, getting the playbook right the first time pays dividends on every future deal. Programmatic acquirers deliver 8.5% TSR vs 3.7% for ad-hoc dealmakers—and that gap comes from building integration as a capability.
When You Probably Don’t Need One
External help isn’t always necessary:
The acquisition is small and simple. Under 20 employees, straightforward systems, no complex regulatory issues. Your internal team can likely handle this with some extra focus.
The target is already on your stack. If the acquired company uses the same CRM, ERP, and email platform you do, “integration” is mostly configuration and access management—not a transformation programme.
You’ve done this before. If you’ve successfully integrated three similar acquisitions, you have the playbooks and experience. You might still need extra hands, but not strategic guidance.
You have genuine internal capacity. Not “we’ll make it work” capacity—actual bandwidth to dedicate to integration without degrading other work. A dedicated internal integration manager with real experience can often deliver as well as an external consultant.
Timeline pressure is low. If you have 18+ months and no urgent reporting requirements, you can afford to learn as you go. Speed is where consultants add the most value.
Questions to Ask Before Hiring
If you’re on the fence, work through these:
- Do we have someone who’s done this before? Not “managed IT” or “led a project”—specifically led post-merger integration. If not, you’re learning on the job.
- What happens if we get it wrong? If the downside is “minor delays,” maybe you can risk it. If it’s “blown synergies and talent exodus,” external help is insurance.
- Can we dedicate full-time resource? Integration is a full-time job for someone—often several people. If you’re expecting existing staff to squeeze it in, quality will suffer.
- How tight is our timeline? The tighter the timeline, the more you need experienced execution. Consultants bring speed.
- Is this a one-time event or the start of a programme? If you’re acquiring once, the cost of learning on the job is a one-time hit. If you’re acquiring repeatedly, building the right foundation pays back on every deal.
What to Look For in a PMI Consultant
If you decide to hire external help, here’s what matters:
Relevant experience. Not just “M&A experience”—experience with deals similar to yours. Mid-market roll-up integration is different from billion-pound corporate mergers. Ask for case studies that match your situation.
Execution capability, not just strategy. Some firms are great at telling you what to do. Fewer are great at actually doing it. Ask where their involvement ends: at the PowerPoint, or at the working system?
Change management as core, not add-on. If change management is a separate workstream with separate fees, they’re treating it as optional. It’s not. The human side is often what determines success or failure.
Clear accountability. Who’s responsible for the overall outcome? If you’re managing three specialist vendors with no one owning the whole picture, you’re the integration manager by default.
Honest about what they don’t do. Good consultants are clear about their boundaries. If they can’t do data migration, they should say so—not muddle through and charge you for their learning curve.
The Real Question
The decision isn’t really “consultant vs no consultant.” It’s “what’s the cost of getting this wrong?”
78% of successful acquirers spend 6%+ of deal value on integration. That’s not a coincidence. The companies that underinvest in integration are the ones that end up in the 83% failure statistic.
A PMI consultant is one way to invest in getting it right. Not the only way—but for deals with real complexity, real stakes, or real time pressure, often the pragmatic one.
Key Takeaways
- PMI consultants work across five areas: strategy, operations, systems, change management, and programme management. Few do all five equally well.
- The market is specialised: Strategy firms for planning, Big 4 for end-to-end, system specialists for platforms, boutiques for mid-market execution.
- You probably need help if: it’s your first acquisition, the deal is complex, the timeline is tight, your team is stretched, or change management will be hard.
- You probably don’t if: the deal is small and simple, the target’s already on your stack, you’ve done this before successfully, or you have genuine internal capacity.
- The real question is risk: What happens if integration fails? If the answer is “significant value destruction,” external help is insurance worth buying.
Want to go deeper? See 50+ Post-Merger Integration Statistics for the full data behind these findings, or download The Roll-Up Integration Playbook for a step-by-step guide.
About PMI Stack: We help roll-ups unify systems, data, and workflows across acquired companies—so their platform runs like one company, not ten. If you’re planning an integration, book a free discovery call.
