How to enhance heavy oil recovery to meet the oil consumption is a popular issue around the world, and it has attracted widespread attention. A two-dimensional visualized model was adopted to study the pore-scale mechanisms and development effects of foam for enhancing oil recovery in steam injection processes for heavy oil. Experimental images visually presented that small bubbles gather together to form bigger foams, thus blocking the small pores and throats and leading to fluid diversion in porous media. As a result, the sweep efficiency was improved from 46.18% to 77.93% after foam injection. Foams could effectively improve the mobility ratio between oil and water and decreased water cut after foam injection, which was significant for decaying the decline of oil production. As for the pore-scale level, after foams were injected into the visualized model, the residual oil caused by steam flooding entered into the main streamline under the disturbance of foams and was carried out by the following displacement fluid. The heavy oil was emulsified into O/W emulsions that had lower viscosity under the action of foams; hence, more trapped oil was mobilized and displaced. As a result, the micro oil displacement efficiency increased from 72.76% to 84.01%. In order to provide a reference for the choice of foam injection, experiments that investigated development effects of cold foam and hot foam were also conducted. Compared with the incremental of oil recovery caused by cold foam, that induced by hot foam was 41.51% higher, demonstrating that the coinjection of steam and foam was more advantageous to heavy oil production.