The Faith singer's mum Lesley Panos died of cancer almost a decade ago and Michael swore he would put on a free show to thank the nurses who eased her pain if he ever toured again.
Michael told the audience of 2,000 nurses at London's Roundhouse venue: "Thank you to every single one of you. I salute you - and this evening is 100% me saying 'Thank you' to you."
Yesterday's show was the last on Michael's sell-out European 25 Live tour - his first tour in 15 years.