Is it possible to use radiofrequency devices to lift saggy breasts?

The short answer is no. Breasts that require uplift need to have skin removed rather than simply tightened and the amount of tightening one can get from radiofrequency is so minor as to be not worth considering in this scenario

You need a formal evaluation by a licensed plastic surgeon and expert in breast lifts, revisions and augmentations to determine what is best for you and your goals.Breast lift surgery can improve a woman's breast shape by repositioning the breast mound at a higher position on the chest and then centering the nipple and areola on the breast itself. If there is enough breast tissue, I can perform a highly aesthetic mastopexy without the addition of further volume by internally rearranging the breast tissue and removing excess skin. If more volume is needed, especially in the upper portion of the breasts, we will discuss the possibility of fat grafting or silicone gel implant placement. The type of incision required for this surgery (circumareolar, “lollipop” or “anchor”) and the lifespan of the lift depends on each patient’s condition, breast tissue, genetics, weight and hormonal fluctuations, and desired results.
Augmentation with mastopexy is a challenging surgery that requires significant experience to create a shape that is youthful, natural, and proportionate to the body, while managing the native tissue as well as fat grafts or implants. When performed properly, it can result in a dramatic improvement to a woman’s breast appearance.
I suggest consulting with a board-certified plastic surgeon and expert in Breast Lifts. - Dr. Cohen

Thank you for your question. Photos would've been helpful. ThermiTight by Arvarti is a radiofrequency device that can tighten the skin by heating the subdermal area all the way around the breast. The small puncture holes are made in the areola with no sign of surgery. The lift is minimal, 1.5-2.0 cm nipple lift. If your breasts are more saggy and the nipple/areolar complex needs to be lifted more than the above, then a short scar or lollipop lift can be done.See a board certified plastic surgeon who can offer multiple options for an in person consultation/evaluation. Good luck.

I am aware of minimally invasive procedure to tighten the skin but have never seen a decent result.  I say don’t waste your money.

Dear JudyTrudy,
radiofrequency won't have affect on breasts. If you have saggy breasts, you will most likely need breast lift in order to improve the shape of your breasts. My preferred lift is a lollipop lift when a periareolar won't do (ie greater than 2cm lift required). The lollipop technique was created by a Canadian plastic surgeon named Elizabeth Hall-Findley and treats the breast as a three dimensional structure instead of two dimensions (anchor - lift). Most importantly it does not require the horizontal component scars that the anchor-lift requires and breasts appear much more natural, lifted, and less boxy. Lastly, the lift lasts longer because the lollipop doesn't rely on the skin to hold the breast up, its actually breast tissue thats being brought together to support the breast and hence improves longevity. 
If you are considering a surgery, I would suggest you to consult a board-certified plastic surgeon. Only after a thorough examination you will get more information and recommendations.
Daniel Barrett, MD
Certified, American Board of Plastic Surgery
Member, American Society of Plastic Surgery
Member, American Society of Aesthetic Plastic Surgery

Radiofrequency treatments done all over the breast can help tighten and lift those breasts which are not too large and heavy nor sag too much.

Hi and welcome to our forum!Unfortunately, the amount of skin tightening of a sagging breast achieved with radiofrequency treatments to the chest will be negligible as the area to shrink is too large by far. Even if it were possible, there is no way to control this theoretic shrinkage. The final shape of the breast would be unpredictable.Surgery is still the only way to achieve a breast lift.Best wishes...

and I don't think it will do much of anything.  If you do explore this further and find a surgeon say it will work, get a written warranty so you know what happens if it doesn't meet your expectations and promised results.  Get some objective measurements that can be used and if someone is able to warranty their work, then go for it.  Threading was introduced a few years ago but I am unfamiliar with its success rate and durability.

At this point, the best and most predictable breast lifts can be achieved only with surgery. There are some devices that advertise skin tightening, but the results are fairly minimal. At this point, the technology probably isn't powerful enough to lift the breasts enough to be effective. Best to consult in person with an American Board of Plastic Surgery certified surgeon who can discuss with you your options for best results.

Internal radiofrequency treayments with Bodytite or Thermi have been proven to lift breasts. It wont lift very droopy breasts but 1 - 1.5 cm of nipple lift have been seen