<p>Granulomatous diseases of the nose and paranasal sinuses (PNS) are rare but present significant diagnostic challenges due to their overlapping features with common sinonasal conditions. Early diagnosis is critical to prevent serious complications, yet clinical and radiological findings often mimic infections, inflammatory diseases, or malignancies. This case series describes four patients with granulomatous diseases of the PNS, including granulomatous invasive fungal rhinosinusitis, granulomatosis with polyangiitis (GPA), and IgG4-related disease. Clinical presentations, diagnostic challenges, treatment strategies, and outcomes were analysed to highlight key learning points. All patients demonstrated complex clinical courses, with initial misdiagnosis in two cases due to misleading serological results. Careful histopathological review, repeat biopsies, and multidisciplinary collaboration were essential in establishing the correct diagnosis. Targeted medical management based on final diagnoses led to favourable outcomes, with no relapses observed during follow-up. Granulomatous diseases of the PNS require a high degree of clinical suspicion, timely tissue diagnosis, and close interdisciplinary coordination. Reliance on serology alone may lead to errors; histopathology remains the cornerstone of diagnosis. Structured diagnostic approaches and vigilant follow-up are critical to improving patient outcomes in these complex cases.</p>