| Abbreviation | Definition |
|---|---|
| NLBPA | Negro Leagues Baseball Players Association |
| NLCSMVP | National League Championship Series Most Valuable Player |
| NLLB | Niagara Little League Baseball |
| NLMB | New Lowell Minor Baseball |
| NLWC | National League Wild Card |
| NMBA | Nanaimo Minor Baseball Association |
| NNOB | No Name On Back |
| NO | Number |
| NOTB | Night Over Thirty Baseball |
| NPB | Nippon Professional Baseball |
| NPBL | Nicaraguan Professional Baseball League |
| NPPB | Newbury Park PONY Baseball |
| NRBB | North Royalton Baseball Boosters |
| NRBC | New Richmond Baseball Club |
| NRBL | Nebraska Reserve Baseball League |
| NSB | North Seattle Baseball |
| NSBA | North Seattle Baseball Association |
| NSBL | North Shore Baseball League |
| NSBL | North Star Baseball League |
| NSFY | No Soup For You |