The on-loan Liverpool midfielder struck 12 minutes from time, shortly after Scott McDonald appeared to have given the Championship's third-placed club the points.
It was the second time in the match the Seasiders produced a rapid response after Ludovic Sylvestre cancelled out McDonald's 15th minute opener.
Boro are now unbeaten in 16 home matches, but a magnificent display from Matt Gilks in the Blackpool goal was a key factor in them slipping three points behind West Ham in the second automatic promotion spot.
Gilks frustrated McDonald and strike-partner Marvin Emnes either side of half-time to leave visiting manager Ian Holloway undoubtedly more satisfied with the point than opposite number Tony Mowbray.
Middlesbrough's unchanged XI took to the field in black armbands in tribute to former goalkeeper Brad Jones, whose five-year-old son died yesterday following a battle with leukaemia.
Gary Taylor-Fletcher returned to the Blackpool attack in the unexpected absence of Lomana LuaLua for the matchday 16.
Stephen McManus was inches away from giving Boro the lead when he planted a header from Barry Robson's free-kick against the post in the eighth minute, but the hosts did not have to wait much longer to gain the advantage.
Robson's delivery - this time from open play - was again inch perfect, allowing McDonald to nod past Gilks.
But Blackpool's start had been largely composed and, after refusing to be knocked out of their stride, the Seasiders drew level in the 21st minute.
Taylor-Fletcher was involved in the build-up, finding Sylvestre on the edge of the area before the French midfielder confidently curled home his first goal for the club.
Gilks was forced to push Joe Bennett's drive out of the top corner after Barry Ferguson lost the ball shortly before the half hour.
Blackpool were profligate in possession once more moments later, leaving Robson to ride a challenge on the edge of the area and fashion an opening. However the Scotland midfielder thumped over with only Gilks to beat.
The visitors' earlier control had become a distant memory and Gilks was called into action once more, thwarting a McDonald header to preserve parity.
Middlesbrough resumed in the ascendancy after the interval and Gilks was called into action at his near post to repel Emnes.
An astonishing double save from Emnes and McDonald followed, before the latter found a way past Blackpool's inspired goalkeeper to re-establish Boro's lead in the 73rd minute.
Sylvestre partially cleared a Robson corner, but when Rhys Williams sent the ball back into the area it fell for McDonald to poach his fourth goal of the season, and a third in two games.
But Holloway's men once again found a rapid and clinical reply.
Substitute Matt Phillips, making his Blackpool return following a successful loan spell at Sheffield United, launched a raid down the right flank and his cross was met emphatically on the volley by Shelvey to leave Boro keeper Jason Steele with no chance.