Workplace Mediation Explained: The Acas Certificate in Internal Workplace Mediation

Not every workplace disagreement needs to end up as a formal grievance. Mediation — a trained, impartial person helping two colleagues work through a disagreement themselves — is increasingly built into UK employers' conflict resolution toolkit, and Acas runs one of the best-known routes into doing it well: the Certificate in Internal Workplace Mediation, or CIWM.

What the CIWM actually trains people to do

The CIWM is explicitly aimed at people managers, team leaders, and worker representatives who want to resolve disagreements within their own organisation — it's not designed for people training to become external or freelance mediators working across different employers. The course covers what causes workplace conflict, how to spot problems early before they escalate into formal complaints, the right timing and methods for stepping in, techniques for managing genuinely difficult conversations, and how to encourage people to actually engage with mediation rather than defaulting straight to a grievance process.

Course structure and accreditation

The CIWM is a five-day accredited programme, delivered either in person or remotely, built heavily around role play and facilitated discussion rather than passive classroom learning — reflecting the fact that mediation is fundamentally a practical, conversational skill rather than a body of knowledge to memorise. The course is accredited by NCFE, a nationally recognised awarding body, and assessed through a combination of written and practical work. Everyone who attends gets a certificate of attendance, and those who pass the assessment receive the formal Certificate in Internal Workplace Mediation (Acas, 2026).

Why organisations train internal mediators rather than always going external

Bringing mediation in-house, rather than relying purely on external mediators for every dispute, has practical advantages: an internal mediator already understands the organisation's culture, policies, and working patterns, and can often be deployed faster than arranging an external mediator from outside. It also tends to be considerably cheaper at scale, since training a handful of internal mediators to handle routine interpersonal disputes is more cost-effective than paying for external mediation every time a disagreement between colleagues needs a structured, impartial conversation rather than a formal process.

How this fits into a wider HR toolkit

Workplace mediation sits alongside, rather than replaces, an organisation's formal grievance and disciplinary procedures — it's most useful for disputes that are genuinely resolvable through conversation, such as personality clashes, communication breakdowns, or misunderstandings between colleagues, rather than serious misconduct or matters with legal implications. Employers building out a wider HR CPD offering often pair internal mediation training with broader people-management development — the kind of grounding covered in Learnsignal's guide to CIPD qualifications — since both skill sets sit squarely within good day-to-day people management rather than specialist employment law practice.

What good mediators bring beyond the course

Completing the CIWM gives someone a structured framework and practised techniques, but organisations that get the most value from internal mediation tend to be selective about who they put through the training in the first place — looking for people who are naturally seen as fair and approachable by colleagues, not just those with capacity in their diary. Mediation only works if both parties trust the person in the room, which is as much about existing credibility within the organisation as it is about the formal training itself.

Mediation and written employment terms

Workplace mediation often surfaces issues that trace back to unclear expectations set out — or not set out — at the start of employment, which is part of why it pairs naturally with getting the basics of the employment relationship right in the first place, including a properly drafted written statement of employment particulars. A dispute over working hours, duties, or reporting lines is sometimes really a dispute about what was actually agreed, and a trained mediator working from clear written terms has a much easier job establishing the facts than one working from two colleagues' conflicting memories of a verbal conversation months earlier.

Choosing who to train as an internal mediator

Because the CIWM is a significant time and financial commitment, most organisations are deliberate about who they put through it rather than opening it up broadly. Common candidates include experienced HR business partners, senior team leaders with a track record of handling difficult conversations well, and trade union or staff representatives who already have credibility across different parts of the workforce. Training a small, carefully chosen group tends to produce better outcomes than spreading the investment thinly across many people who may never actually get called on to mediate a real dispute.

Frequently asked questions

Is the CIWM suitable for someone who wants to mediate outside their own organisation?
No — it's specifically designed for internal workplace mediation within your own organisation, not for training external or freelance mediators.

How long does the Acas CIWM course take?
It's a five-day accredited programme, available either in person or remotely.

Does mediation replace the formal grievance process?
No — mediation works alongside formal procedures and is best suited to resolvable interpersonal disputes, not serious misconduct or matters with legal implications.