Abstract: Objective: To determine the associations of protein-specific anti-malondialdehyde acetaldehyde (MAA) antibodies with prevalent and incident rheumatoid arthritis-interstitial lung disease (RA-ILD). Methods: Within a multicenter, prospective cohort of U.S. Veterans with RA, RA-ILD was validated by medical record review of clinical diagnoses, chest imaging, and pathology. Serum antibodies to MAA-albumin, MAA-collagen, MAA-fibrinogen, and MAA-vimentin (IgA, IgM, and IgG) were measured by a standardized ELISA. Associations of anti-MAA antibodies with prevalent and incident RA-ILD were assessed using multivariable regression models adjusting for established RA-ILD risk factors. Results: Among 2,739 RA participants (88% male, mean age 64 years), there were 114 prevalent and 136 incident RA-ILD cases (average time to diagnosis: 6.6 years). Higher IgM anti-MAA-collagen (per 1 SD: aOR 1.28 [1.02-1.61]), IgA anti-MAA-fibrinogen (aOR 1.48 [1.14-1.92]), and IgA (aOR 1.78 [1.34-2.37]) and IgG (aOR 1.48 [1.14-1.92]) anti-MAA-vimentin antibodies were associated with prevalent RA-ILD. In incident analyses, higher IgA (per 1 SD: aHR 1.40 [1.11-1.76]) and IgM (aHR 1.29 [1.04-1.60]) anti-MAA-albumin antibody concentrations were associated with increased ILD risk. Participants with IgA (aHR 2.13 [1.16-3.90]) or IgM (aHR 1.98 [1.08-3.64]) anti-MAA-albumin antibody concentrations in the highest quartile had an approximate 2-fold increased risk of incident RA-ILD. Across all isotypes, anti-MAA-fibrinogen, -collagen, and -vimentin antibodies were not significantly associated with incident RA-ILD. Conclusions: Protein-specific anti-MAA antibodies to collagen, fibrinogen, and vimentin were associated with prevalent RA-ILD. IgA and IgM anti-MAA-albumin antibodies were associated with a higher risk of incident RA-ILD. These findings suggest that MAA-modifications and resultant immune responses may contribute to RA-ILD pathogenesis.