We study the Josephson diode effect arising from geometric and phase-structural properties in a Kitaev-ladder Josephson junction composed of two parallel spinless $p$-wave chains coupled by interleg hopping $t_{\perp }$. The junction is governed by two phases: the superconducting phase difference across the junction, $\theta$, and the interleg phase difference, $\varphi$. For $\varphi \notin \{0,\pi \}(mod2\pi )$, the effective time-reversal-like constraint is broken. Together with the absence of leg-exchange symmetry, this yields the condition for a Josephson diode response. A detailed analysis identifies different tunneling contributions to the Josephson current-phase relation: a shifted, non-sinusoidal contribution and an approximately unshifted, sinusoidal contribution. Their interference provides a mechanism for unequal positive and negative critical currents. The class-D Pfaffian invariant identifies the parameter regimes in which protected Majorana zero modes occur at the ladder ends. Bogoliubov-de Gennes calculations reveal a pronounced dome-like dependence of the diode efficiency $\eta$ on $t_{\perp }$ with $\eta \to 0$ for $t_{\perp }\to 0$ and for large $t_{\perp }$, with a maximum at intermediate coupling, tunable by $\varphi$. Within this minimal topological ladder model, the results clarify how geometry, symmetry breaking, and topology combine to enable a superconducting diode effect in a one-dimensional system.