Kubica will aid the development of the Hinwil-based outfit, having previously raced in F1 for the team in its BMW Sauber guise – taking his sole win in F1 for the team at the 2008 Canadian GP.
The signing of Kubica has been aided by chief sponsor Orlen, which will become Alfa's title partner in 2020.
Having confirmed his departure from Williams at the end of 2019, Kubica had been strongly linked with a development role at Racing Point and Haas, but has now confirmed a deal with Alfa, which he is expected to supplement with a race seat in DTM with BMW.
"This team holds a special place in my heart and I am pleased to see some faces still here from my years in Hinwil," he said.
"Time and circumstances are obviously different, but I am convinced that I will find the same determination and hunger to succeed."
Kubica previously held a similar role with Williams before being promoted to the race line-up and Alfa are looking forward to linking up with the Pole.
Team principal Fred Vasseur said: "We are delighted to welcome Robert back home and we cannot wait to start working with him.
"He is a driver that needs no introduction: one of the most brilliant in his generation and one who displayed the true meaning of human determination in his fight to return to racing after his rallying accident.
"His feedback will be invaluable as we continue to push our team towards the front of the grid."
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