A series of 3-azabicyclo[3.1.0]hexanes and cyclopropa[a]pyrrolizidines spiro-fused to acenaphthylene-1(2H)-one and aceanthrylene-1(2H)-one frameworks have been studied for their in vitro antiproliferative activity against human erythroleukemia (K562), cervical carcinoma (HeLa), melanoma (Sk-mel-2), osteosarcoma (U2OS), as well as murine melanoma (B16) cell lines. Using confocal microscopy, it was found that cultivation with the tested spiro-fused compounds led to the disappearance of stress fibers (granular actin was distributed diffusely in the cytoplasm in up to 56% of treated cells) and decrease in filopodia-like deformations (up to 69% after cultivation), which indirectly suggests a decrease in cell motility. The human melanoma cell line scratch test showed that these cells lose their ability to move after cultivation with the tested spiro-fused compounds and do not fill the scratched strip. This was also supported by docking simulations with actin-related targets (PDB ID: 8DNH, 2Q1N). Using flow cytometry, the impact on the mitochondrial membrane potential showed that the tested compounds led to a significant increase in the number of cells with decreased mitochondrial membrane potential from 10% for the control up to 55–80% for the cyclopropa[a]pyrrolizidine adducts. The obtained results support the antitumor effect of the tested spiro-compounds and encourage the extension of the study in order to improve their anticancer activity as well as reduce their toxicological risks.