We investigate the domination polynomial of the co-maximal graph $Γ(\mathbb{Z}_n)$ related to the ring of integers modulo $n$. Such a polynomial encodes domination sets of all possible sizes, a NP-hard problem for general graph. We give exact formulas for prime powers, integers with two distinct prime divisors, and products of three distinct primes. A prime-support decomposition gives a finite explicit formula for arbitrary $n$, including repeated prime factors. Further results determine the highest coefficients, the precise threshold beyond which every vertex subset dominates, and the number of non-dominating subsets. We discuss unimodality and log-concavity, and derive justified bounds for nonzero domination roots using the Eneström--Kakeya theorem.

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