Due to their low cost, lightweight, antifouling and anticorrosion properties, polymer heat exchangers (PHXs) are replacing metal heat exchangers in a variety of applications. Nowadays, 3D printing technology is gaining increasing attention to fabricate these PHXs. This study employs Fused Deposition Modeling (FDM), a popular 3D printing technique, to construct PHXs from ABS material (i.e., Acrylonitrile Butadiene Styrene) and investigates some of the important parameter effects on their heat transfer performance under varied operating conditions. Experiments were performed for the shell side flow rates varying from 0.6 to 3 L/min and tube side flow rates varying from 1.2 to 3.6 L/min. The overall heat transfer coefficient (U) ranged from 66 to 121 W/m2 K in these printed PHXs, thereby showing the effect of printing and operating conditions. The results showed that the printing temperature (PT) and tube wall thickness (WT) had a significant influence on the thermal performance of PHXs while the printing speed (PS) demonstrated a trivial effect. Apart from enhancing the thermal performance, higher printing temperature also resulted in lowering the dimensional variations. The roughness analysis of the tubes revealed that the PHXs with smooth surfaces interestingly had better heat transfer performance than tubes with rougher surfaces. Further, such smooth surfaces were realized with a high printing temperature. These findings conclude that higher roughness does not necessarily improve the thermal performance of layered PHXs, contrary to continuous structure HXs. Also, high printing temperature, small wall thickness, and low printing speed are conducive conditions to produce printed PHXs with greater thermal performance, and reduced roughness and dimensional variations. This study can act as a guideline for printing precise and high-performance PHXs. © 2023, The Author(s), under exclusive licence to Springer-Verlag London Ltd., part of Springer Nature.