Do I need to fill out and sign capital gains form if I filed electronically?

[Critter]

When you efile you sign electronically ... there is nothing for you to ink sign. 

[TomYoung]

Your question might very well have left out important information. 

If there's a missing prefatory statement along the lines of "I summarized all my security trades" - meaning you didn't enter each and every sale into TurboTax but only entered summary proceeds and cost figures for all your trades - then you do need to send in to the IRS a substitute Form 8949, (the 1099-B provided by the broker will probably suffice), accompanied by IRS Form 8453.  You do have to fill out some information on that form, but it doesn't need to be signed.