INTRODUCTION: An intracholecystic papillary neoplasm (ICPN) of the gallbladder is a newly established disease concept. Here, we report a case of ICPN with associated invasive carcinoma, manifesting with multiple polyps in the markedly enlarged gallbladder. PRESENTATION OF CASE: A 73-year-old female patient visited a clinic because of weight loss. A movable 15-cm mass was palpable in the right lower quadrant and she was referred to our hospital. Contrast-enhanced computed tomography (CT) showed that the gallbladder was markedly enlarged and multiple polyps were diffusely spread throughout it. DISCUSSION: ICPN with associated invasive carcinoma, as distinguished from the ordinary type gallbladder adenocarcinoma, was introduced in the 2019 WHO tumor classification. Individual data of its characteristics will be accumulated and further research on oncological behavior will be conducted. CONCLUSION: We experienced a case of ICPN with associated invasive carcinoma, presenting with a palpable mass in the right lower quadrant.