Both sides struggled to find their feet in a poor first half but Gareth Ainsworth almost put QPR ahead with an audacious lob before the break.
The home side did take the lead when Marc Nygaard headed home Paul Furlong's cross but Smith equalised when he curled in a superb left-footed shot.
Furlong missed two late chances for QPR before Derby had Darren Moore sent off for a second booking before the end.
Derby manager Terry Westley
"That's my 13th game in charge, and the responsibility of trying to keep a club of Derby County's stature in this division is draining.
"There is so much going on and the club is in a transitional period.
"But at least now we know where we are next season."
QPR: Jones, Kus, Shittu, Evatt, Milanese, Ainsworth, Donnelly (Furlong 58), Bailey, Langley, Cook, Nygaard.
Subs Not Used: Cole, Santos, Lomas, Howell. Booked: Bailey.
Goals: Nygaard 59.
Derby: Camp, Jackson, Moore, Nyatanga, Michael Johnson, Smith, Barnes (Peschisolido 64), Bolder (Idiakez 64), Seth Johnson, McIndoe (Holmes 64), Lisbie. Subs Not Used: Poole, Edworthy.
Sent Off: Moore (88).
Goals: Smith 67.
Ref: T Kettle (Berkshire).