Randomized trials of coaching show a moderate average effect, with signs of publication bias
A meta-analysis of 37 randomized controlled trials (39 samples, n = 2,528) finds coaching improves leadership and personal outcomes, with a best estimate of g = .59, and reports significant publication bias.
Finding
What the study measuredAcross 39 randomized coaching samples (n = 2,528), coaching had statistically significant effects on all leadership and personal outcomes studied, with a best estimate of g = .59. Effects were larger for self-reported than for observed outcomes, larger for qualified coaches in non-leadership applications, somewhat larger for female coachees, and depended little on the total length of the assignment. The authors found significant publication bias.
Authors' interpretation
What the authors concludeThe authors read the results as clear new evidence that coaching is effective across a range of applications, and they say the publication bias they found was expected. They explain the moderator pattern with a model of how coach and coachee regulate each other's behavior.
| Question type | effect |
|---|---|
| Population and setting | Randomized controlled trials of workplace and executive coaching published in English, 1994 to 2021; Workplace and executive coaching |
| Intervention | Workplace and executive coaching (details per trial not given in the abstract) |
| Comparison | Randomized control groups (details not given in the abstract) |
| Follow-up | Not reported in the abstract |
| Outcomes | Leadership outcomes; Personal outcomes |
| Measures | Self-reported and observed outcome measures (types not itemized in the abstract) |
| Effect size and uncertainty | Best estimate g = .59 (described by the authors as moderate). The confidence interval is not given in the abstract. |
| Limitations | Read from the abstract only, so confidence intervals, heterogeneity and per-outcome results are not available here. The authors report significant publication bias, so the average effect may be overstated. The abstract mentions five confirmed predictions but describes only four. |
| Funding and conflicts | Not stated in the abstract. |
| Replication | Not applicable (synthesis of prior trials). |
| Source reuse terms | Publisher copyright; no open-access version found on 2026-10-24. |
Figures reported, with their location in the source
- g = .59: Best estimate of the overall effect (Abstract)
- 37 RCTs, 39 samples, n = 2,528: Evidence base (Abstract)
Read the source
de Haan, E., & Nilsson, V. O. (2023). What can we know about the effectiveness of coaching? A meta-analysis based only on randomized controlled trials. Academy of Management Learning & Education, 22(4). https://doi.org/10.5465/amle.2022.0107
Verification record
- Status
- human-verified
- Access level
- abstract-only
- Date accessed
- 2026-10-24
- Tool-checked
- 2026-10-24
- Automated retraction check
- 2026-10-24: Crossref record has no update, correction or retraction notices (Crossref carries Retraction Watch data). Owner to confirm.
- Human-verified
- 2026-10-24
- Retraction status
- none-found (checked 2026-10-24); Owner check: "Retraction check: r-0001, none-found"
- Last reviewed
- 2026-10-24
How to cite this entry
consultants.coach. (2026). Randomized trials of coaching show a moderate average effect, with signs of publication bias (Entry r-0001, version 2026-10-24 00:00:00 -0400 EDT). https://consultants.coach/research/r-0001/
Original source: de Haan, E., & Nilsson, V. O. (2023). What can we know about the effectiveness of coaching? A meta-analysis based only on randomized controlled trials. Academy of Management Learning & Education, 22(4). https://doi.org/10.5465/amle.2022.0107
Change log
- : First published after human verification.
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Our commentary
consultants.coach editorial viewThis is the strongest design base available on coaching effectiveness, because it pools randomized trials only. Two cautions matter for practice. First, publication bias means the true average effect is probably smaller than .59. Second, self-reported results ran higher than observed ones, so a sponsor asking for proof of impact is better served by observed or third-party measures than by coachee self-ratings. We read only the abstract, so we cannot report the uncertainty around the estimate.