The appointment ends Last’s 23-year stay with Hull FC as a player and coach following Brett Hodgson’s arrival as head coach of the Black and Whites.
Last spent part of 2020 as interim head coach, guiding Hull to within 80 minutes of the Grand Final but was overlooked for the permanent role.
He will work with head coach Chris Chester and Willie Poching at Trinity.
Last said: “I’m really excited about the challenge. I obviously had 23 years at Hull FC and that chapter ended in a good fashion, with no bridges burnt, so to speak.
“I spoke to Chris on the phone and he stressed that he wanted to get me on board, which is brilliant for me. Chris is someone I respect and I love the project and the way he’s looking to do things next year.
“It’s the right time for me to spread my wings and gain some different experiences, and I don’t think there’s anywhere better for me to do that than at Wakefield Trinity. I’m really excited about getting started.”
Hull FC chairman Adam Pearson paid tribute to Last, saying: “He is held in the highest regard by everyone here and we were eager for him to stay, so much so that we tailored a role to his skill-set that we feel there was no-one better than Andy to undertake.
“However, we appreciate the stage Andy is at in his career and understand the reasons for his decision, which he has thought long and hard about, and he leaves with our blessing and very best wishes for the future.”