He said: "I look back on my years as captain of Surrey with great pride but that's a chapter of my life that is now finished. I'm looking forward to coming back to Hove and picking up where I left off.
"This was the club I wanted to come to. Both parties felt it would be a good move."
Hamilton-Brown added that the good memories of his earlier time with Sussex was also important to his decision.
"A lot of the guys I played with before are now senior members in the side.
"It's exciting; there's a good age range in the side and a lot of exciting cricketers. I'm looking forward to hopefully playing a part in taking the side forward," he said.
"There is a very homely and loyal feeling (here) and that is something that's had an impact on the decision I've made because that loyalty is something you really treasure.
"I hope to have a good winter and get myself ready technically, physically and emotionally, ready to have a big impact on a season where I think Sussex can challenge (for trophies)."
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