But the federal MP isn't entirely ruling it out.
Cullen, who serves as NDP Leader Tom Mulcair's House leader in Parliament, says there's a 15-to-20 per cent chance he'll move to the provincial arena.
Cullen's name is being bandied about as a possible successor to Adrian Dix, who formally announced last week his intention to step down as B.C. NDP leader.
Dix's leadership has been in doubt since last May's provincial election, when Liberal Premier Christy Clark managed to win re-election with a comfortable majority, defying public opinion polls which had predicted a Dix victory.
Cullen — whose engaging manner and sense of humour helped propel him to a third-place finish in the 2012 federal NDP leadership contest — says his name has come up as a prospective provincial contender because he fits the profile some New Democrats are looking for: young and rural.
Cullen is 41 and represents the riding of northern B.C. riding of Skeena-Bulkley Valley.
"The encouragement has been really nice and humbling," he said in an interview.
Nevertheless, he added: "I've been pretty cool to the idea, honestly."
Cullen said he's put together a list of pros and cons and the cons outweigh the pros.
"That's not a good sign."
Among the cons, "B.C. tends to be pretty hard on its leaders, of all stripes ... It's pretty tough, it's very personal and sometimes implicates your family and that's a place I can't go. I won't bring my family into attacks and subject them to that."
Moreover, Cullen said he's reluctant to give up his "great role" as House leader federally, which he described as a key element of the party's "incredibly important project" to win government in the next election in 2015.
"I think a lot of things count on us getting it right."
Also on HuffPost