Tailoring the optoelectronic properties of semiconductor quantum dots is essential for designing functionalized nanoscale devices. In this work, we use first-principles calculations to study the optoelectronic properties of small penta-graphene quantum dots (PGQDs) with various edge-functionalized groups, including hydrogen, halogen (fluorine, chlorine, and bromine), and hydroxyl functional groups. It is evident that these quantum dots, especially those passivated by hydrogen atoms, are thermally stable in vacuum. Moreover, the larger the quantum dots, the more negative the formation energy on stability could reach, thus forming thermodynamically more stable quantum dots. All investigated PGQDs exhibit semiconductor properties. Their bandgaps decrease with an increase in the size of the quantum dots, resulting from the hybridization of sp² and sp³ carbon atoms and from the charge depletion or accumulation between the passivated atoms and the principal components upon interactions. Concurrently, this study aims to explain the optical absorption anisotropy induced by the edge-functionalized groups of PGQDs under multiple incident light polarizations. These results highlight the use of edge-functionalized groups to develop the next generation of optoelectronic devices.