<p>The effects of the topology of cyclic polymers at surfaces and interfaces are described and discussed in this review. The topics include those at the air‒water interface, micellization, phase transition, and adsorption to nanoparticles. Surface tension studies revealed that the interfacial activity of cyclized polymers is greater than that of their linear counterparts because of an increase in the molecular density at the air‒water interface. Moreover, the micellization enthalpy and entropy (Δ<i>H</i>_mic and Δ<i>S</i>_mic) and lower critical micelle temperature (<i>T</i>_CMT) were found for cyclic polymers, where the hydrophilic/hydrophobic ratio also significantly influenced. In addition, cyclic poly(ethylene glycol), <i>c</i>-PEG, can interact strongly with gold nanoparticles (AuNPs) and bovine serum albumin (BSA), whereas no such effects were found for linear PEG. The red color of an AuNPs dispersion vanished when BSA was added to complexes of AuNPs/<i>c</i>-PEG to form aggregates. In this context, silver nanoparticles (AgNPs) have not been proven to be capable of consistent PEGylation despite their usefulness in biological applications. <i>c</i>-PEG was found to physisorb onto AgNPs to effectively PEGylate and improve dispersion stability under physiological circumstances, long-term exposure to white light, and high temperature. Consequently, the generation of new functional materials and their applications can be facilitated by the effects of cyclization, which makes the use of a polymer topology feasible for the logical design of polymeric materials.</p>