The large-billed scrubwren is found from near Cooktown in northern Queensland to Kinglake and the Dandenong Ranges, near Melbourne, Victoria. The distribution of the 3 subspecies corresponds to 3 discontinuous areas within its overall range: the nominate subspecies Sericornis magnirostra magnirostra is found from the Clarke Range, inland of Mackay, Queensland to East Gippsland in Victoria; S. m. viridior is found in northeast Queensland from Mt Amos, south of Cooktown, to the Paluma Range National Park, near Townsville; and S. m. howei is found in West Gippsland and the Strzelecki Ranges of southern Victoria. Its preferred habitat is rainforest in the tropics and wet sclerophyll forest in temperate areas. It is sedentary and more common in the north of its range.