Let R be a commutative ring with 1 ∈ R and R * be the multiplicative group of its units. In 1969, Nagell introduced the concept of an exceptional unit, namely a unit u such that 1 − u is also a unit. Let Z n be the ring of residue classes modulo n. In this paper, given an integer k ≥ 2, we obtain an exact formula for the number of ways to represent each element of Z n as the sum of k exceptional units. This generalizes a recent result of J. W. Sander for the case k = 2.