While accurate second-order P-δ analyses are necessary components of slender masonry wall design (particularly at high axial loads), comprehensive second-order analyses are excessively computationally demanding for designers. Approximate second-order analysis techniques are prescribed by standards in lieu of more sophisticated analyses; one such technique permitted in the Canadian (S304-14) and American (TMS 402/602-22) standards is the moment magnifier method. The moment magnifier method “magnifies” the primary moment on a wall by a factor which is a function of the eccentricities of the end moments (e1/e2) and the ratio of the applied axial load to the critical buckling load (Pf/Pcr). However, a recent study has shown that the moment magnifier method is unconservative for many combinations of e1/e2 and Pf/Pcr—an undesirable quality in a standard-prescribed simplified analysis technique. Subsequent comparison between the moment magnifier method and numerical second-order analysis revealed that e1/e2 and Pf/Pcr were not the only variables influencing wall total moments. That is, two walls with the same e1/e2 and Pf/Pcr could have significantly different total moment values as predicted numerically, while the moment magnifier method would predict the same total moment both times. Additionally, the moment magnifier method has not been verified to provide reasonable total moment estimates for typical North American masonry construction; by contrast, such verifications have occurred in the reinforced concrete literature. A parametric study is thus conducted on the influence of wall height, wall thickness, and magnitude of end eccentricity on wall total moment values; variable ranges were carefully selected to be of relevance to Canadian masonry construction. Lateral loads were not considered. The study revealed that wall height and the magnitude of the end eccentricity strongly influenced wall total moment; wall thickness minimally influenced results. Varying these additional parameters while holding constant e1/e2 and Pf/Pcr values yielded total moment values which differed by up to 39%. Furthermore, compared to numerically obtained total moments, the moment magnifier method overestimated and underestimated total moments by up to 100% and 17.5%, respectively. A more rational and robust moment magnifier method is thus needed, capable of accurate load predictions for future standards.