Classical molecular dynamics (MD) with the adaptive intermolecular reactive bond order (AIREBO) potential is used to examine the effects of elongated tetravacancies (575757-666- 5757 defects) on the mechanical properties of graphene sheets containing such defects. In these computer simulations, stress-strain dependences, maximum elastic strain, maximum plastic strain and tensile strength are revealed which characterize a graphene sheet containing an elongated tetravacancy in two tensile tests. In the first and second tests, tensile load was applied parallel and perpendicular to the long axis of the defect, respectively. It is revealed that the mechanical characteristics of graphene are significantly influenced by elongated tetravacancies.