The effects of intrinsic point defects including antisites, vacancy as well as alloying solutes Mo, Re, W and Ta on \{111\} antiphase boundary (APB) energy of γ'-Ni₃Al have been investigated via first-principles calculations. The configurational stability of APB with a single point defect in as-mentioned types is evaluated first and the results show that all the point defects are energetically favorable near APB, while Mo substitutions are relatively unfavorable. Ni_Al antisites reduce APB energy and most Al_Ni antisites enhance it, mainly resulting from decreased/increased amount of Ni-Al bonds and ordering energy near Al_Ni/Ni_Al antisites. Single alloying solutes show positive effects on APB energy except substituting Ni sublattice sites in APB plane. Ta and W substituting Al site at APB plane with larger APB energy could improve the strength of γ'-Ni₃Al efficiently. ELF analysis on the bonding of alloying solute and the nearest neighboring Ni atom shows stronger chemical strength than bonding of Al and Ni atoms. Vacancy diminishes the APB energy, especially for Al vacancy at APB plane, whose reduced effect even cannot be offset by alloying solutes. However, calculations of formation energy show that Al vacancy-alloying solute defects have relatively poor stability. Further results show that Al vacancy at APB plane preferentially migrates to more stable Ni vacancy at adjacent plane of APB plane due to the low migration barriers. The negative effect of Al vacancy on APB energy is accordingly mitigated. Besides, the low migration barriers partially provide the theoretical evidence for solute segregation to APB.