---
schema_version: "secwatch.filing_event.v1"
accession: "0001436126-23-000042"
form_type: "8-K"
ticker: "MG"
cik: "0001436126"
company_name: "Mistras Group, Inc."
filed_at: "2023-10-10T23:59:59+00:00"
generated_at: "2026-06-10T02:13:05.617892+00:00"
event_type: "leadership"
sentiment: "neutral"
materiality_score: 0.8
calibrated_materiality_score: 0.8
confidence: "high"
source: SEC EDGAR
---

# Mistras Group: Founder Vahaviolos retires as Exec Chairman; CEO Bertolotti terminated; Stamatakis named Interim CEO

## Summary
- Founder Sotirios Vahaviolos retires as Executive Chairman, becomes Chairman Emeritus.
- CEO Dennis Bertolotti terminated without cause, effective immediately; resigns from Board.
- Manuel Stamatakis named Chairman and Interim CEO; receives $500k base salary and 250k stock options.
- James Forese appointed Lead Director and Chair of Corporate Governance Committee.
- Board will conduct a search for a permanent CEO using a leading executive search firm.

## SEC filing metadata
- accession: 0001436126-23-000042
- form_type: 8-K
- ticker: MG
- cik: 0001436126
- company_name: Mistras Group, Inc.
- filed_at: 2023-10-10T23:59:59+00:00
- event_type: leadership
- sentiment: neutral
- materiality_score: 0.8
- calibrated_materiality_score: 0.8
- confidence: high
- sec_items: 5.02, 5.05, 7.01, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/1436126/000143612623000042/0001436126-23-000042-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1436126/000143612623000042/mg-20231009.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001436126-23-000042
- JSON: https://secwatch.observer/filing/0001436126-23-000042.json
- Plain text: https://secwatch.observer/filing/0001436126-23-000042.txt

## Key facts
- Executive change
  Sotirios Vahaviolos retired as Executive Chairman at Mistras Group, Inc..
  - Action: retired
  - Role: Executive Chairman
  source text: On October 9, 2023, Sotirios Vahaviolos, Executive Chairman of the Board (the “Board”) of Mistras Group, Inc. (the “Company”), retired as Executive Chairman but will remain on the Board as Chairman Emeritus.
  evidence_url: https://www.sec.gov/Archives/edgar/data/1436126/000143612623000042/0001436126-23-000042-index.htm
- Executive change
  Manuel N. Stamatakis was appointed as Chairman of the Board at Mistras Group, Inc..
  - Action: appointed
  - Role: Chairman of the Board
  source text: the Board elected Manuel N. Stamatakis (currently the Company’s Lead Director, Chairman of the Corporate Governance Committee and member of the Audit, Compensation, and Environmental, Social and Safety Committees) to serve as Chairman of the Board to succeed Dr. Vahaviolos.
  evidence_url: https://www.sec.gov/Archives/edgar/data/1436126/000143612623000042/0001436126-23-000042-index.htm
- Executive change
  Dennis Bertolotti departed as President and Chief Executive Officer at Mistras Group, Inc..
  - Action: terminated without cause
  - Role: President and Chief Executive Officer
  source text: On October 9, 2023, the Board also approved the termination without cause of Dennis Bertolotti as the Company’s President and Chief Executive Officer, effective immediately.
  evidence_url: https://www.sec.gov/Archives/edgar/data/1436126/000143612623000042/0001436126-23-000042-index.htm
- Executive change
  James J. Forese was appointed as Lead Director and Chairman of the Corporate Governance Committee at Mistras Group, Inc..
  - Action: appointed
  - Role: Lead Director and Chairman of the Corporate Governance Committee
  source text: the Board appointed James J. Forese, currently a member of the Board and Chairman of the Audit Committee, as Lead Director and Chairman of the Corporate Governance Committee.
  evidence_url: https://www.sec.gov/Archives/edgar/data/1436126/000143612623000042/0001436126-23-000042-index.htm
- Executive change
  Manuel N. Stamatakis was appointed as Interim President and Chief Executive Officer at Mistras Group, Inc..
  - Action: appointed
  - Role: Interim President and Chief Executive Officer
  source text: the Board appointed Mr. Stamatakis to serve as interim President and Chief Executive Officer until a permanent President and Chief Executive Officer has been appointed.
  evidence_url: https://www.sec.gov/Archives/edgar/data/1436126/000143612623000042/0001436126-23-000042-index.htm
- Governance Changes
  Mistras Group, Inc.: Board granted Manuel Stamatakis a waiver of the code of ethics and code of conduct related to a conflict of interest with his position at CME (effective 2023-10-09).
  - Change: code of ethics
  - Effective: 2023-10-09
  source text: In connection with Mr. Stamatakis’ appointment as interim President and Chief Executive Officer, the Board granted Mr. Stamatakis a waiver of the Company’s code of ethics and code of conduct to the extent that his position with CME, as described in Item 5.02 above, is a conflict of interest under the Company’s code of ethics or its code of conduct.
  evidence_url: https://www.sec.gov/Archives/edgar/data/1436126/000143612623000042/0001436126-23-000042-index.htm

This AI-assisted summary is a reading aid. Review the linked SEC EDGAR filing before relying on any specific claim.