Objective To use polyamidoamine dendrimers (PAMAM) loaded with sh-miR-34a for constructing PAMAM/sh-miR-34a nanocomplexes and to observe its inhibitory effect on the proliferation, invasion and metastasis of malignant melanoma A375 cells. Methods Particle size analyzer was used to investigate the potential and size of the constructed PAMAM/sh-miR-34a nanocomplex, and sh-miR-34a enrichment capability was determined by gel electrophoresis assay. The intracellular uptake of PAMAM/sh-miR-34a by A375 cells was investigated using sh-miR-34a labeled by rhodamine. CCK8 method was used to determine the inhibitory effect of the nanocomplex against A375 cell proliferation. Transwell assay was used to determine the inhibition effect of nanocomplex against A375 cell migration and invasion. Western blotting analysis was used to examine the inhibitory effect of PAMAM/sh-miR-34a on the protein expression of pAkt, pRb, and pERK1/2 in A375 cells. Results PAMAM loaded with sh-miR-34a could form stable nanocomplexes. The intracellular uptake of PAMAM/sh-miR-34a by A375 cells was the highest when N/P=20 (P<0.05). PAMAM effectively mediated sh-miR-34a entry into A375 cells, inhibiting the cell proliferation, invasion and metastasis and blocking the protein expression of pAkt, pRb, and pERK1/2 in A375 cells. Conclusion PAMAM can enwrap sh-miR-34a and inhibit malignant melanoma A375 cells.