The Guinness World Records website officially posted it as record on Saturday.
President Abdul Hamid congratulated the people and said this achievement would inspire the whole nation.
Private mobile operator Robi Axiata Limited with the help of Bangladesh Army created the human flag with 27,117 people on Dec 16 at old airport in the capital.
The Guinness Records auditors were present to oversee the attempt of making red, green human flag.
Among the participants were army personnel who held up the red centre while students made up the green rectangle.
The previous record was set by 24,200 youths in Pakistan, a country with which Bangladesh fought a bloody nine-month war to gain independence.