Antonyms of adj worthwhile

1 sense of worthwhile

Sense 1
worthwhile -- (sufficiently valuable to justify the investment of time or interest; "a worthwhile book")

INDIRECT (VIA worthy) -> unworthy -- (lacking in value or merit; "dispel a student whose conduct is deemed unworthy"; "unworthy of forgiveness")

Similarity of adj worthwhile

1 sense of worthwhile

Sense 1
worthwhile -- (sufficiently valuable to justify the investment of time or interest; "a worthwhile book")
       => worthy (vs. unworthy) -- (having worth or merit or value; being honorable or admirable; "a worthy fellow"; "a worthy cause")