Using density functional theory calculations, we have analyzed nonlinear optical properties of a series of T-graphene quantum dots differing in their shape and size. Electronic polarizability and first-order and second-order hyperpolarizability of these systems are investigated and shed light on their stability and electronic properties. Negative cohesive energy shows that they are energetically stable. The effect of size and incident frequency on their nonlinear responses are comprehensively discussed. Most of the systems exhibit a strong NLO response, and it is enhanced in the presence of an external field. All these systems show absorption maximum ranging from UV to visible window. Overall, this theoretical framework highlighted the nonlinear optical properties of T-graphene quantum dots that may provide valuable information in designing potential NLO materials.