Tarry defied Labour leader Keir Starmer’s orders calling for his frontbench not to attend picket lines during the latest strike.
Around 40,000 RMT union members are understood to have walked out on Wednesday with talks between the RMT and Network Rail over pay, pensions and conditions deadlocked.
Tarry, MP for Ilford South in London, joined striking workers at London’s Euston station. He told the BBC he was "backing transport workers who are on strike" and "the travelling public".
Several junior Labour frontbenchers tweeted their solidarity with the striking rail workers but did not join Tarry in appearing on the picket line.
Transport secretary Grant Shapps the strikes were "completely wrong".
