| 2021 Cary Challenger II | |
|---|---|
| Date | 13–19 September |
| Edition | 8th |
| Surface | Hard |
| Location | Cary, North Carolina, United States |
| Champions | |
| Singles | |
 Mitchell Krueger | |
| Doubles | |
| William Blumberg / Max Schnur | |
The 2021 Cary Challenger II was a professional tennis tournament being played on hard courts. It was the 8th edition of the tournament which was part of the 2021 ATP Challenger Tour. It took place in Cary, North Carolina, United States between 13 and 19 September 2021.
| Country | Player | Rank1 | Seed |
|---|---|---|---|
| USA | Tennys Sandgren | 91 | 1 |
| USA | Denis Kudla | 92 | 2 |
 ITA | Salvatore Caruso | 113 | 3 |
 AUS | Alex Bolt | 146 | 4 |
 TPE | Jason Jung | 166 | 5 |
| USA | Mitchell Krueger | 175 | 6 |
| USA | Michael Mmoh | 181 | 7 |
| USA | Bjorn Fratangelo | 190 | 8 |
The following players received wildcards into the singles main draw:
Garrett Johns 
Luca Stäheli Zachary Svajda The following players received entry from the qualifying draw:
Mitchell Krueger def. Bjorn Fratangelo 6–4, 6–3. William Blumberg / Max Schnur def. Stefan Kozlov / 
Peter Polansky 6–4, 1–6, [10–4].