Vanadyl petroporphyrins purified from a North American petroleum vacuum residue are used in experiments probing the interfacial phenomena of the petroporphyrins as well as asphaltene-petroporphyrin mixtures. Water-oil emulsion stability as a proxy for film strength is measured using the centrifugal method. Interfacial tension and elasticity of asphaltene and petroporphyrin films are recorded over tens of hours using an interfacial dilational rheometer. Film thicknesses of asphaltene films with and without petroporphyrins are estimated by fitting multiple models to small-angle neutron scattering curves. UV-visible spectroscopy is used to compare petroporphyrin content in the interfacial and bulk material of emulsions. Petroporphyrins are shown to be surface active and have significant effects on asphaltene film development. Surface-active petroporphyrins form monolayers at the interface with very low tension and high dilatational elasticity. However, this high elasticity does not translate to film strength. Being more surface active than asphaltenes, petroporphyrins may displace the first layer of asphaltenes that adsorb at the interface. However, thick asphaltene films that kinetically stabilize the emulsified water droplets still form. Monodisperse populations of petroporphyrins are prone to precipitation and therefore do not stabilize the interface or form an elastic film.