Atherosclerosis is a chronic inflammatory disease of the arteries that can lead to heart attack and stroke. Atherosclerotic plaques build up over time due to an inflammatory response to the presence of lipids in the blood. A key immune cell in plaque development is monocytes, which differentiate into macrophages as they enter the vessel wall. In this work, we develop an agent-based model of early plaque development to investigate the impact of monocyte lineage on plaque development. Previous research has shown a correlation between monocyte lineage and a differentiated macrophage’s ability to efflux lipid and emigrate from the plaque. We investigate this here and show under what conditions plaques arise in the vessel wall. The model presented here can serve as a platform for future hypothesis generation on macrophage involvement in plaque development to be tested.