Let \({\mathbb {H}}^n\) denote the Heisenberg group, identified with \({\mathbb {R}}^d \times {\mathbb {R}},\) where \(d = 2n\) and \(n \in {\mathbb {N}}.\) We consider the spherical maximal operator \({\mathcal {M}}\) associated with the sphere \(S^{d-1}\) embedded in the horizontal subspace \({\mathbb {R}}^d \times \{0\}\) of \({\mathbb {H}}^n.\) It is known that \({\mathcal {M}}\) is bounded on \(L^p({\mathbb {H}}^n)\) if and only if \(p \in (\frac{d}{d-1}, \infty ].\) In this paper, we establish a restricted weak type (p, p) estimate at the endpoint \(p = \frac{d}{d-1}\) for \({\mathcal {M}},\) provided \(d \ge 3.\)
