The third particle occurred at the interface of contacting surfaces is common situations in relative motion part. This study involved developing an analysis framework to investigate the contact characteristics in the full range of 3-body mixed lubrication. Conventional 2-body mixed lubrication is a special case of 3-body mixed lubrication analysis with particle size of zero. This study revealed that the values of real contact area, film thickness, contact mode, and the solid contact load in 3-body contact were larger than those in ideal 2-body contact in mixed lubrication, and they increased with an increasing particle size or density under the study conditions. The initial stages and transition processes of four types of 3-body contact modes under mixed lubrication were significantly different for different particle sizes and densities. The size of the third particle increased the values of both minimum and maximum values, λmin and λmax, of film parameter in the mixed lubrication regime. The particle density did not have a significant effect on the λmax value in mixed lubrication. Higher particle density led to a larger λmin value in mixed lubrication. The conventional film parameter, λ, was not a sufficient indicator of the different lubrication regimes in 3-body contact.