She made the advice when her British counterpart David Cameron asked for her opinion about the matter in a meeting on the sidelines of G7 Outreach Meeting in Japan on Friday.
Cameron said there was an ongoing debate in the UK over the issue, Foreign Secretary Shahidul Haque told reporters after the meeting.
The Bangladesh prime minister said leaving a union in this era of globalisation and communication needs more thought, Haque said.
She said the people of the UK were to take the decision, but she thinks the UK should be in the EU, Haque said.
She said British MPs with Bangladeshi-origin Tulip Siddiq, Rupa Huq and Rushanara Ali were working to raise awareness among the British to remain in the EU.
The two heads of government also discussed bilateral issues. Hasina urged more investment from the UK.
Haque said Cameron asked Hasina what the mystery behind Bangladesh’s achieving 7 percent GDP growth was, and he praised her leadership.
The UK prime minister also said his country wanted to be a development partner of Bangladesh.
Foreign Minister AH Mahmood Ali accompanied Hasina during the meeting.