Helik headed Barnsley ahead on 59 minutes and Woodrow wrapped up victory from the penalty spot in injury time.
Tykes manager Valerien Ismael will have been equally pleased by Polish centre-back Helik's contribution at the other end of the pitch, as his team kept their first clean sheet in 12 outings.
Conor Chaplin made a lively start for Barnsley, brushing the sidenetting with a fierce 20-yard effort before putting the ball in the net after latching on to a lofted Alex Mowatt pass only to be flagged offside.
For Rovers, Kayne Woolery headed straight at Tykes keeper Brad Collins at the far post following a left-wing free kick from Otis Khan.
Determined away defending then saw Lee O'Connor and George Ray make excellent blocks to repel shots on goal from Chaplin and Callum Styles.
Ray was also in the right place to kick a weak Dominik Frieser effort off the line after Scott Davies had raced out of his goal to smother a Woodrow chance.
A diving Woodrow header, following good work from Frieser down the left, went on to bounce narrowly wide of goal.
But Tranmere had the first half's best chance to break the deadlock on 42 minutes when Woolery burst past Mads Anderson down the right flank and sent in a low cross that James Vaughan collected before spinning and firing a low shot that required Collins to demonstrate sharp reflexes.
Barnsley began to assert themselves more at the start of the second period and, after Chaplin's edge-of-the-box effort lacked the conviction to extend Davies, the Rovers keeper could do little to prevent Helik from breaking the deadlock just before the hour.
The 25-year-old defender rose high to meet Herbie Kane's left-wing cross to claim his fourth goal of the season with a powerful downward header from 10 yards out.
Ismael's men remained on the front foot after the goal, but Kane and Chaplin both cleared the crossbar from distance.
Khan's execution was also too high from a Tranmere free kick but a set-piece delivery from the same player led to a well-struck Woolery volley that came closer to an equaliser.
Late on, a wayward Styles strike hit unwitting team-mate Victor Adeboyejo and ricocheted wide.
Woodrow then drilled a one-on-one opportunity straight at Davies before getting his chance to take his season's goal tally into double figures in the fifth minute of stoppage time.
Jay Spearing fouled Luke Thomas to concede a penalty that Woodrow drilled to Davies' right as the Rovers keeper dived in the opposite direction, putting a seal on Barnsley's seventh win in 10 contests.