Actions speak louder than words, as the saying goes -- so, while "Arrow" star Stephen Amell said he wasn't down with actors going on strike, his actions say the exact opposite.

Stephen had a picket sign in hand as he marched Friday with his fellow actors in NYC, which is interesting coming on the heels of his appearance on "TMZ Live."

He told us he supports his union, SAG-AFTRA, but totally disagreed with the union leadership's decision to go on strike, believing there are better ways to negotiate a good deal with the studios.

Stephen also told us he had a meeting scheduled with SAG honchos, and based on these images of him picketing with his wife and fellow actress Cassandra Jean ... it would seem the union brass convinced him to publicly get on board with the strike.

Some of Stephen's former cast members were also busy supporting the actors' strike on the left coast -- Katie Cassidy, Katrina Law, Willa Holland, Caity Lotz, Kirk Acevedo and Juliana Harkavy were all on the picket lines in the L.A. area. Even the show's executive producers came to show their support.

Stephen's shift is pretty dramatic ... last week he told us he wanted to see the union get back to the negotiating table, rather than continue the work stoppage.

He also claimed that although he's one of the only actors speaking out against striking, many of his colleagues secretly contacted him to express their support for his view.