Introducing temporary markers for imaging studies is an idea, which in the proper clinical settings can be advantageous for patient compliance and in selected cases where a permanent marker is nondesirable. Hence, we developed injectable marker formulation using a biodegradable “pasty polymer” of poly­(ricinoleic acid-co-sebacic acid) (PSA:RA) containing iodixanol and iron oxide as contrast agents that can serve as a visual marker for the region suspected to have tumor growth. The goal of this work is to noninvasively evaluate the visibility, shape, and degradation of the injectable PSA:RA formulation using magnetic resonance imaging (MRI), computed tomography (CT), and ultrasound (US). Prescreening of the marker formulation was performed under MRI and CT scanning using agar gel phantom models with poly­(l-lactide-co-ε-caprolactone) (PCL:LA) solid inserts (clips) that contained varying combinations of the contrast agents. The contrast agent combination with the PCL:LA clip that had the best visibility in both MRI and CT was selected and additionally tested as in PSA:RA formulation. Further, we evaluated the PSA:RA marker placement in bovine liver and poultry muscles. The PSA:RA formulation is predictable with good MRI, CT, and US visibility and shows no in vivo systemic toxicity symptoms when implanted subcutaneously in mice. Further, the advantage of PSA:RA formulation is its undefined shape and ease of injecting through a small gauge needle, making it possible to reach into the regions of the body.