Pseudocellulitis, manifesting as erythema, warmth, and tenderness of the lower extremities, is a recently recognized cutaneous adverse reaction (CAR) associated with the use of pemetrexed, a multi-targeted folate antagonist. This reaction typically manifests bilaterally, helping to distinguish pemetrexed-induced pseudocellulitis from a bacterial cellulitis. We present a case of unilateral pemetrexed-induced pseudocellulitis. The patient was initially treated for cellulitis but failed to respond adequately to antibiotics, prompting a biopsy that showed the characteristic findings of pemetrexed-induced pseudocellulitis. Pemetrexed-induced pseudocellulitis is important to recognize as it may be dose-limiting or necessitate treatment modification. Furthermore, increased awareness of this CAR can help clinicians avoid unnecessary antibiotic use.