The 30-year old left Bradford City when his deal expired at the end of last season and has now signed a one-year deal with the Well after training with them over the past three weeks.
"It seems as if I have been here for a while already," said Ramsden.
"I went to Portugal with all the lads at the start of the month and that was really good in terms of getting to know everyone as you're spending 24 hours a day with them all.
"Everyone is making me feel very welcome and it's nice to get everything sorted. I am really looking forward to the challenge ahead."
Ramsden kicked off his career with Sunderland in 2001 and has since spent time with Notts County (on loan), Grimsby Town and Rochdale before heading to Bradford in 2009. He reunites with Motherwell boss Stuart McCall who managed him for about a year at Valley Parade.