Beadle, 30, joins the Blues for a third spell at the Turnbull Ground, having scored 42 goals in 148 appearances for the club between 2008 and 2013.
"I'm really excited to get going and grab this opportunity with both hands," said Beadle.
"It's a club I know really well having played there before, I actually think I played some of my best football there and scored a lot of goals.
"I go with a point to prove that I'm still good enough to play at this level and I'm hungry and ready to embrace this fresh challenge.
"I've had a year in the wilderness really with the lack of playing time I was getting at Boro and I'm ready to go again now, get fit in training and hit the ground running."
Beadle added that playing under boss Chris Hardy was a major factor in him joining the Blues, despite interest from Pickering Town.
"The manager [Chris Hardy] is one of the main reasons I'm joining Whitby Town," he added.
"I've heard plenty of good things about him from a lot of people and I was excited after talking to him this week before signing.
"He seems to be a positive bloke and I need that now - to be in a positive dressing room with a positive manager who will back me and encourage me to play.
"I obviously had a look at the fixture list and the Scarborough game is the one that caught my eye. It'll certainly be a quiet Christmas for me leading up to New Year's Day and I really will have a point to prove there."
Boss Hardy insists it was a no-brainer to bring Beadle back to the club after he left Boro.
"First and foremost, Jimmy brings a good level of experience for someone of his age and he's familiar with the Football Club," said Hardy.
"He can play in a number of roles, which is a bonus obviously, but I spoke with Jimmy and he sees his best position as centre midfielder and that's where we're looking to improve. But it helps that he can also play in more advanced areas if needed.
"He's a little different to the normal of type of player we're usually bringing in from the higher sides' academies, and will come in and know the expectations of the club and how to handle a matchday at this level."