The LetS/LetA two-component system (TCS) is part of a regulatory network responsible for core physiological processes of Legionella pneumophila including morphological differentiation and virulence. It is widely understood that the response regulator (RR) LetA is an essential factor for L. pneumophila replication within Acanthamoeba castellanii. To date, LetA transposon mutants in strains JR32 and Paris have been the primary mode of studying how LetA impacts L. pneumophila. With increased risks of polar effects from transposon insertions and limited information regarding how a LetA deficiency affects Lp02 biology, the relationship between LetA and A. castellanii infection was revisited. An unmarked LetA mutant (Lp02 ∆letA), a transposon insertion mutant (Lp02 ∆letA::Km) and complemented and overexpressed derivatives were characterized. Strains Lp02 ∆letA and Lp02 ∆letA::Km retained their ability to replicate within A. castellanii, contrary to previous reports. However, strains harbouring multicopy LetA possessed an enhanced ability to replicate within the host. Furthermore, LetA overproduction altered growth in liquid culture with cells exhibiting a truncated morphology. LetA has been reported to impact L. pneumophila sodium sensitivity and pyomelanin secretion. Our mutants showed different phenotypes with bacteria exhibiting parental levels sodium sensitivity and pyomelanin production. While overexpression of LetA did not impact the catabolism of pyomelanin, it did decrease resistance to salinity stress. In summary, a loss of LetA showed little to no effect on Lp02 physiology, whereas LetA overexpression altered several traits of this bacterium. Taken together, our findings support the notion that LetA is an important regulator of Legionella pathogenesis.