Alfonso played James' on-screen son, Carlton Banks, in the hit American sitcom and earlier this week he shared photos from the memorial, describing the occasion as a "celebration of James' life".
One of the touching pictures shows the majority of the Fresh Prince cast gathered together for the first time in years, wearing black and dark blue outfits.
Alfonso's caption read: "We said goodbye to the amazing James Avery last night. I was honoured to host the memorial for Barbara Avery. It was a wonderful tribute and celebration of his life. He will be deeply missed."
Those present included James' second on-screen wife Daphne Maxwell Reid and his on-screen children Karyn Parsons and Tatyana Ali, who played Hilary and Ashley Banks.
The popular Banks butler Geoffrey (played by Joseph Marcell) was also at the memorial, as well as James' Barbara Avery, who is seen stood in the centre of the group shot.
Absent from the proceedings was lead Fresh Prince star Will Smith, although he did pay tribute to his former on-screen uncle on Facebook earlier this month.
Will wrote: "Some of my greatest lessons in acting, living and being a respectable human being came through James Avery."
James played judge Philip Banks in more than 140 episodes of the popular American sitcom and maintained a close relationship with his co-stars after filming ended in 1996.
He died at the age of 68 on New Year's Eve (31 December) after reportedly suffering complications following heart surgery.
Alfonso went on to upload a couple more images from the memorial, including one of Karyn and Tayana with his newborn son, as well as one of James at his wedding to wife Angela last October.
He wrote beside the wedding snap: "Here's another photo of James from our wedding. It is still hard to believe he is no longer with us. It feels like yesterday when I would drop by his dressing room and learn about some of the great Jazz music he would listen to. Such a warm, inspiring, wonderful man."
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