Much of the recording for Willennium took place at producer DJ Jazzy Jeff's A Touch of Jazz Studios in Smith's hometown of Philadelphia, Pennsylvania, where nine songs were tracked.

[4] Production for Willennium was handled by a number of producers who had previously worked on Big Willie Style, including executive producers DJ Jazzy Jeff and Poke & Tone, Keith Pelzer and Sauce, as well as a number of new contributors: Rob Fusari, Kay-Gee, "Little" Louie Vega, Rodney "Darkchild" Jerkins and more.

[3] In addition to upbeat songs, the album has also been described as featuring ballads (including "No More") and Latin pop sounds (on "La Fiesta").

Club describes the album negatively as composed of "slick, soulless party jams, old-school nostalgia, chemistry-free duets ... and cheerful materialism".

[3] Erlewine noted that "Smith isn't quite as convincing when it comes to slow [songs]", but claimed that "the heart of the album lies in the up-tempo dance numbers, since they're what make Willennium irresistible".

[3] A review published by NME was similarly positive, claiming that Willennium is evidence of Smith's dominance of the hip-hop genre at the time, and praising songs such as "I'm Comin'", "Freakin' It" and "Da Butta".

[12] Writing for the website PopMatters, however, Cynthia Fuchs describes Willennium as "generic", commenting unfavorably on various lyrics, themes and performances.

[16] However, they described the single "Will 2K" as "utterly awful" and "gimmicky", and claim that Smith "is overwhelmed by the cluttered production" on the record.

[14] Willennium was a commercial success, the album debuted at number five on the US Billboard 200 chart, selling 187,000 copies in its first week.

[18] In December 1999, the album had been certified double platinum by the Recording Industry Association of America (RIAA) for sales of over two million copies.