The Irish broadcaster's voice filled the vast church as recordings from his archive were played.
He died in January following a battle with cancer.
The biggest names in broadcasting turned out for the event, A Service Of Thanksgiving For The Life And Work Of Sir Terry.
They included Dermot O'Leary, Claudia Winkleman, Fearne Cotton, Tess Daly, Joanna Lumley, Gloria Hunniford, Jimmy Carr, Eamonn Holmes, Ruth Langsford, Matt Baker and Jo Whiley.
Strictly Come Dancing co-host Winkleman said afterwards: "I thought the service was beautiful."
The event included tributes from Sir Terry's children and a poem especially co-written for the occasion by actress Lumley, in which she compared Sir Terry's voice to "an aural, newly ripened peach".
The service was conducted by the Dean of Westminster, Very Rev Dr John Hall, who said in his Bidding: "Terry Wogan was a legend in his own lifetime.
"Still feeling his loss, we come today to remember. But may we above all celebrate his life, give thanks to God for his gifts, and pray that the generous, warm spirit he demonstrated so powerfully might never fade away in this country, in these islands."
Archbishop Emeritus of Westminster Cardinal Cormac Murphy-O'Connor read 1 Chronicles 16: 8-13, 23-24 and Stevie Spring, Chairman of BBC Children in Need, read Mark 10: 13-21.
Hymns included Be thou my vision and O Praise ye the Lord.
Premier's Dave Rose was there and told the News Hour it was a moving event: "It was really a combination of his talents as a broadcaster and the warmth with which he live his life for other people".