The 6`5” forward was the Quakers’ top scorer last season, netting 18 league goals in a productive first season at Blackwell Meadows.
Prior to linking up with current York City manager Martin Gray at Darlington, the 23-year-old came through the youth ranks at Carlisle United before a series of loan moves, including the likes of Falkirk and Wrexham, saw Beck included in the Scotland under-19 set-up.
Despite missing some of the current season through injury, the Sunderland-born striker played all but one of the Quakers’ league games during 2016/17 before opting to join Simon Weaver’s side.
Beck, who scored during his side’s visit to The CNG Stadium last season, joins up with North-East duo Liam Agnew and Andrew Nelson at Harrogate, while linking up again with Josh Falkingham, who was also with Darlington last season.
Weaver told his club`s official website: "We are all delighted to sign Mark. We know that from playing against him and watching him play several times that he is a big threat in front of goal.
"His physical presence will complement the current players within our set-up, and at 23 years of age his best years are ahead of him."
Darlington manager Tommy Wright added: “Things happened quickly over the weekend. Mark has a release clause in his contract that Harrogate activated”.