| Document and Entity Information | Dec. 07, 2023 |
| Cover [Abstract] | |
| Amendment Flag | false |
| Entity Central Index Key | 0001860424 |
| Document Type | 8-K |
| Document Period End Date | Dec. 07, 2023 |
| Entity Registrant Name | Onex Falcon Direct Lending BDC Fund |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 814-01405 |
| Entity Tax Identification Number | 86-3687484 |
| Entity Address, Address Line One | 21 Custom House Street |
| Entity Address, Address Line Two | 10th Floor |
| Entity Address, City or Town | Boston |
| Entity Address, State or Province | MA |
| Entity Address, Postal Zip Code | 02110 |
| City Area Code | (617) |
| Local Phone Number | 412-2700 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | true |
| Entity Ex Transition Period | false |
