Each year, the Group for Research and Assessment of Psoriasis and Psoriatic Arthritis (GRAPPA) holds a trainee symposium adjacent to the GRAPPA annual meeting. The target audience for this meeting includes trainees in rheumatology, dermatology, and related fields. The 2021 GRAPPA Trainee Symposium focused on challenges in the diagnosis and assessment of psoriatic arthritis (PsA). During the meeting, speakers focused on identification of psoriasis (PsO), the differential diagnosis for both PsO and PsA, diagnostic errors and pitfalls, physical examination in PsA, patient-reported outcomes and composite measures in the assessment of PsA, and the patient perspective on diagnosis and assessment, followed by a panel discussion. This paper summarizes the content discussed at the meeting.