The Reds midfielder says he will 'miss the banter' but has wished the 24-year-old all the best for the future.
Once an England defender, the 24-year-old can play both at centre-back and right-back, although injuries hampered what was a sharp rise through the ranks at Liverpool.
And Kelly will be missed on Merseyside, as support from former team-mate Lucas shows.
@MartinKelly1990 good luck ticky lad, I will miss the banter but I wish everything goes well for you.— Lucas Leiva (@LucasLeiva87) August 14, 2014
Kelly will now look to rebuild his career at Selhurst Park after falling out of favour at Anfield.
Even the future of Lucas is uncertain, however, with the Brazilian being linked with a move to Napoli throughout the summer.
For now at least, the midfielder remains a part of the Liverpool setup and was the first Reds player on social media to wish Kelly good luck.
Liverpool's Ryan McLaughlin was next to follow, congratulating Kelly on Twitter.
Congrats and All the best @MartinKelly1990 on his move to crystal palace!— Ryan McLaughlin (@RyanMcL2) August 14, 2014
Will Lucas remain a Liverpool player this season?