Background/Objectives: Inflammatory and oxidative-stress-related processes contribute to post-myocardial infarction (MI) remodeling and may influence long-term cardiovascular outcomes. Recent findings have highlighted the potential role of non-coding RNAs in regulating these processes. LncRNA MALAT1 acts as a ceRNA that “sponges” miR-146a, reducing its ability to repress downstream targets such as COX-2. The aim of this study was to assess MALAT1 and miR-146a expression in PBMCs and plasma COX-2 in controls and patients six months post-MI. In addition, we investigated whether MALAT1 rs3200401 and miR-146a rs2910164 variants were associated with MI susceptibility, MALAT1 and miR-146a expression, plasma COX-2 levels, and left ventricle (LV) echocardiographic parameters. Methods: The study included 534 patients and 381 controls for genetic analyses, while expression analyses were performed in a subset of 89 patients and 39 controls. TaqMan™ assays were used for genotyping and for quantification of MALAT1 and miR-146a expression. Plasma COX-2 levels were measured using ELISA. Results: Compared to controls, patients had higher MALAT1 expression, whereas lower miR-146a expression was observed only in unadjusted analyses. Plasma COX-2 levels were higher in patients with advanced heart failure (NYHA III–IV) compared with NYHA I-II. The rs3200401 TT genotype was more frequent in patients, whereas rs2910164 genotype distributions were similar between groups. The rs3200401-rs2910164 TG allele combination was associated with increased MI risk. Conclusions: MALAT1 may serve as a potential long-term biomarker of post-MI molecular alterations, whereas the role of miR-146a requires further investigation in larger cohorts. The rs3200401 variant may represent a genetic marker associated with MI susceptibility and adverse LV remodeling. Further studies are needed for confirmation.