The exposure of marine mammals to phthalates has received considerable attention due to the ubiquitous occurrence of these pollutants in the marine environment and their potential adverse health effects. The occurrence of phthalate metabolites is well established in human populations, but data is scarce for marine mammals. In this study, concentrations of 17 phthalate metabolites were determined in liver samples collected from one hundred (n = 100) by-caught harbor porpoises (Phocoena phocoena) along the coast of Norway. Overall, thirteen phthalate metabolites were detected in the samples. Monoethyl phthalate (mEP), mono-iso-butyl phthalate (mIBP), mono-n-butyl phthalate (mBP) and phthalic acid (PA) were the most abundant metabolites, accounting for detection rates ≥ 85%. The highest median concentrations were found for mIBP (30.6 ng/g wet weight [w.w.]) and mBP (25.2 ng/g w.w.) followed by PA (7.75 ng/g w.w.) and mEP (5.67 ng/g w.w.). The sum of the median phthalate metabolites concentrations that were found in the majority of samples (detection rates > 50%) indicated that concentrations were lower for porpoises collected along the coastal area of Bodø (Nordland), Lebesby (Finnmark) and Varangerfjord (as compared to other coastal areas); these areas are among the least populated coastal areas but also the most distant (>700 km) from offshore active oil and gas fields. The monomethyl phthalate metabolite (mMP) was detected in 69% of the samples, and to our knowledge, alongside with PA, this is the first report of their occurrence in marine mammals. PA, as the non-specific marker of phthalate exposures, showed a statistically significant negative association with the body mass and length of the harbor porpoises. Among the phthalate metabolites, statistically significant positive associations were found between mBP and mIBP, mMP and mEP, PA and mEP, mIBP and mono(2-ethyl-5-oxohexyl) phthalate (mEOHP), mIBP and mono(2-ethyl-5-hydroxyhexyl) phthalate (mEHHP), mBP and mEHHP, mono-n-nonyl phthalate (mNP) and PA, and between monobenzyl phthalate (mBzP) and mNP. To our knowledge, this is the first study on the biomonitoring of 17 phthalate metabolites in harbor porpoises.