Cranston, 58, said he was worried that people might compare the two roles, reported CBS online.
"Oh, that's not anywhere near as good as 'Breaking Bad.' I didn't want to have that conversation," the actor said.
Cranston, who is currently up for a Tony Award for playing President Lyndon B Johnson in the Broadway play 'All the Way', said he read the 'Godzilla' script at his agent's urging and that's what changed his mind.
In this latest Hollywood adaptation, Cranston plays a nuclear scientist who becomes obsessed with what caused the destruction of a nuclear power plant in 1999.
'Godzilla' is now playing in theatres.