Fission of membrane-bound organelles requires membrane remodeling processes to enable and facilitate the assembly of the scission machinery. Proteins of the PEX11 family were shown to act as membrane elongation factors during peroxisome proliferation. Furthermore, through interaction with fission factors these proteins coordinate progression of membrane scission. Using a biochemical approach, we determined the membrane topology of PEX11γ, one of the three human PEX11 proteins. Analysis of mutated PEX11γ versions, which localize to peroxisomes revealed essential domains for membrane elongation including an amphipathic region and regulatory sequences thereof. Through pegylation assays and in vivo studies, we establish that the PEX11γ sequence encloses two membrane anchored domains, which dock an amphipathic region onto the peroxisomal membrane thereby regulating its elongation. The interaction profile of PEX11γ and mutated versions reveals a rearrangement between homo- and heterodimerization and association with fission factors. We also demonstrate the presence of the mitochondrial fission factor Mff on peroxisomes and its interaction with PEX11 proteins. Our data allow for assumptions on a molecular mechanism for the process of peroxisome proliferation in mammalian cells, that i) PEX11γ is required and acts in coordination with at least one of the other PEX11 proteins to protrude the peroxisomal membrane, ii) PEX11 proteins attract both Mff and hFis1 to their site of action and, iii) the concerted interaction of PEX11 proteins provides spatiotemporal control for growth and division of peroxisomes.