Two-dimensional semiconducting systems, such as quantum wells and transition metal dichalcogenides, are the foundations to investigate low dimensional light-matter interactions 1,2 . To date, the study of elementary photoexcitation, namely the exciton, in 2D semiconductors with intrinsic magnetic order remains a challenge due to the lack of suitable material platforms 3,4 . Here, we report an observation of excitons coupled to zigzag antiferromagnetic order in the layered antiferromagnetic insulator NiPS3 using both photoluminescence and optical reflection spectroscopy. The exciton exhibits a linewidth as narrow as ~350 µeV with near unity linear polarization in the photoluminescence spectrum. As the thicknesses of samples is reduced from five layers to bilayers, the photoluminescence intensity is drastically suppressed and eventually vanishes in monolayers, consistent with the calculated bandgap being highly indirect for both bilayer and monolayer 5 . Furthermore, we observed strong linear dichroism over a broad spectra range, which shares the same optical anisotropy axis, being locked to the zigzag direction, as the exciton photoluminescence. Both linear dichroism and the degree of linear polarization in the exciton photoluminescence decrease as the temperature increases and become negligible above the Néel temperature. These observations suggest both optical quantities are probes of the symmetry breaking magnetic order parameter. In addition, a sharp resonance in the linear dichroism spectrum is observed with an energy near the exciton photoluminescence. There exist over ten exciton-A1g phonon bound states on its high energy side, which likely result from the strong modulation of the ligand-to-metal charge transfer energy by strong electron-lattice interactions. Our work establishes NiPS3 as a new 2D platform for exploring magnetoexciton physics with strong correlations, as well as a building block for 2D heterostructures for engineering physical phenomena with time reversal symmetry breaking.