Dissolved　organic　matter　(DOM)　plays　a　critical　role　in　determining　the　quality　of　wastewater　and　the　safety　of　drinking　water.　This　is　the　first　review　to　compare　two　types　of　popular　DOM　monitoring　techniques,　including　absorption　spectroscopy　and　fluorescence　excitation-emission　matrices　(EEMs)　coupled　with　parallel　factor　analysis　(PARAFAC)　vs.　Fourier　transform　ion　cyclotron　resonance　mass　spectrometry　(FT-ICR-MS),　for　the　applications　in　wastewater　and　drinking　water　treatments.　The　optical　techniques　provide　a　series　of　indices　for　tracking　the　quantity　and　quality　of　chromophoric　and　fluorescent　DOM,　while　FT-ICR-MS　is　capable　of　identifying　thousands　of　DOM　compounds　in　wastewater　and　drinking　water　at　the　molecule　level.　Both　types　of　monitoring　techniques　are　increasingly　used　in　studying　DOM　in　wastewater　and　drinking　water　treatments.　They　provide　valuable　insights　into　the　variability　of　DOM　composition　in　wastewater　and　drinking　water.　The　complexity　and　diversity　of　DOM　highlight　the　challenges　for　effective　water　treatments.　Different　effects　of　various　treatment　processes　on　DOM　are　also　assessed,　which　indicates　that　the　information　on　DOM　composition　and　its　removal　is　key　to　optimize　the　treatment　processes.　Considering　notable　progress　in　advanced　treatment　processes　and　novel　materials　for　removing　DOM,　it　is　important　to　continuously　utilize　these　powerful　monitoring　tools　for　assessing　the　responses　of　different　DOM　constituents　to　a　series　of　treatment　processes,　which　can　achieve　an　effective　removal　of　DOM　and　the　quality　of　treated　water.　©　2020