The most commonly discussed topic at the present time is the fluid flow in a channel having a porous area, as it is of practical importance for petroleum extraction, frequently isolated irrigation, coolant circulation, biofluid transportation in living organisms, and industrial cleaning systems. An investigation of heat transfer characteristics of unsteady magnetohydrodynamics oscillatory two‐immiscible fluid flow of Casson fluid (CF) and ferrofluid (FF) in a long‐infinite horizontal composite channel is performed analytically. The channel is divided into two regions. Region I is occupied by a porous region with CF, while Region II is a clear region filled with FF. The mathematical system of coupled partial differential equations is solved analytically considering the two‐term periodic and nonperiodic functions. The influences of physical parameters such as CF parameter, porosity parameter, nanoparticles volume fraction, Hartmann number, periodic frequency parameter, oscillations amplitude, and pressure on momentum as well as heat transfer are presented through graphical illustrations (two‐dimensional along with three‐dimensional) and in tabular form using the MATHEMATICA program. Four different shaped nano‐size ferroparticles are used in this study. The investigation of four different nanosized ferroparticles exhibits that the momentum transfer is higher when brick‐shaped nanosized ferroparticles are added to the base fluid, water. It is also observed that thermal performance enhances in the case of brick‐shaped nanosized ferroparticles compared to the blade, cylinder, and platelet‐shaped nanosized ferroparticles. It is observed that the dispersion of brick‐shaped nanosized ferroparticles is recommended in base fluid water for greater thermal performance through a horizontal channel.