This paper presents control-oriented models, describing the dynamics of the in-cylinder conditions (ICCs) at intake valve closing (IVC), for multi-cylinder Diesel engines. Such models are based on multi-cylinder Diesel engines equipped with dual-loop exhaust gas recirculation (EGR) systems. As the thermodynamic boundary conditions for Diesel engine combustion, ICCs at IVC play critical roles for controlling combustion, particularly advanced combustion modes whose sensitivities to ICCs are very high. Grounded in physical principles, control-oriented ICC dynamic models were developed to describe the multi-cylinder characteristic and the coupling effects among the ICC quantities (i.e. in-cylinder gas mass, gas temperature, and oxygen fraction at IVC). The effectiveness of the developed control-oriented model was validated by comparing with a high-fidelity, 1-D computational, GT-Power engine model.