The 'Bad Liar' hitmaker gave her four-year-old sibling Gracie a pep talk beside the sea on Monday as she encouraged her to be "fearless" and use her voice to make a difference when she grows up because the "truth" will inspire others.
Taking to her Instagram account, the 25-year-old singer uploaded a short black-and-white video of her talking to Gracie as the youngster said: "I'm not scared."
To which Selena replied: "I know because you're fearless, right? You're not scared of anything, right?," before giving her youngster sister an encouraging high five.
She accompanied the sweet clip with the caption: "I will forever let my sister know she is strong, bold and beautiful. She will be raised to know her voice matters. She is going to understand the importance behind being a leader and inspire others by her truth."
Selena's inspiring words come just months after the pop star underwent a kidney transplant after her organs started shutting down as a result of her battle with Lupus.
She was rushed into hospital in May and placed on a kidney transplant list after the autoimmune disease mistakenly attacked her kidneys, but she managed to have the surgery a few weeks later after she found a willing donor in her friend Francia Raisa.
The 'Hands To Myself' hitmaker first revealed she'd been diagnosed with Lupus in 2015 and, one year later, took time out from her pop career to deal with "anxiety, panic attacks and depression" that the life-threatening illness had also caused.
As well as Gracie, Selena also has three-year-old sister Tori, who will no doubt receive the same pep talk when she's slightly older and can understand her words of wisdom.