The combination of properties of boron nitride nanotubes (BNNTs) makes them desirable building blocks for the development of functional macroscopic materials with unprecedented electronic and mechanical features. However, these properties have not been fully exploited because their chemical inertness hampers their processing. One solution is to covalently functionalize the BNNTs to assist in their individualization, dispersion, and processing. Here, we show that dodecyl chains can be covalently attached to BNNTs through the Billups-Birch reaction using lithium and 1-bromododecane as reagents. By combining thermogravimetric and spectroscopic analyses, we were able to verify the presence of the alkyl chains that chemically graft to the outermost wall of the nanotubes, as well as unveil the sp2 to sp3 rehybridization. The hydrophobic addends change the dispersibility and individualization of BNNTs in various organic solvents, which we envision will allow the manufacturing of sophisticated materials such as polymer and ceramic nanocomposites with enhanced strength and thermal stability. Furthermore, because of the inherent thermal stability of BNNTs, the alkyl moieties can be easily removed at high temperatures in air without oxidizing the nanotubes. This chemical functionalization provides a straightforward way to tune the properties of BNNTs, which until now has proven to be a formidable undertaking.