The defence secretary said the UK had sent “intelligence personnel” to the region to help get them out.
His comments, in an interview with Sky News this morning, came as Israel warned the 1.1 million living in north Gaza to leave their homes ahead of an expected ground offensive.
Hamas is known to have taken hostages from Israel into Gaza during its initial attacks on the country last weekend.
Asked by presenter Mark Austin if there were British nationals among those taken, Shapps said: “It seems very likely that there are. We don’t have exact data on that for obvious reasons, but within Gaza there will also be Brits or possibly be people with dual nationalities as well.
“The prime minister has spoken to the Egyptian president about using that border to get people out. The situation is far from clear ... we’ve sent additional intelligence personnel in order to assist with those types of operations.”
Austin said: “So just to be clear, there could be British nationals being held hostage in Gaza and you are sending experts in hostage taking to help out the authorities. Is that true?”
The defence secretary replied: “What I can tell you is it is highly likely - no one will know for sure - there are either British nationals or people with joint-nationality involved in the hostages situation.”
However, Shapps said he did not know “the exact numbers” of British nationals involved.
The Foreign Office has this morning updated its advice to British citizens in Gaza.
It said: “The Israeli military announced on the morning of 13 October that the entire population of Gaza north of Wadi Gaza should relocate to southern Gaza within the next 24 hours.
“We advise following this advice issued by the Israeli authorities. We recognise this a fast-moving situation that poses significant risks.”