The 37-year-old was heard by Australian Fox Sports viewers calling Pietersen a "cunt" when he thought he was off air while commentating at Lord's.
Former England captain Strauss later made an apology, saying: "I apologise unreservedly, particularly to Kevin Pietersen. I am mortified and profusely sorry."
The comments were not heard by viewers watching the MCC v Rest of the World fixture on Sky Sports, but the broadcaster later released a short statement, which read: "Earlier comments were made during a break of play, which were heard overseas. We apologise for the language issued."
MCC went on to beat the Rest of the World by seven wickets in the Lord's bicentenary celebration match.