The event was decided on the final hole when United States' Beth Allen only managed a bogey as her Spanish rival scored par for a 10-under total.
Walker, 32, produced a brilliant eagle on the 18th from 138 yards to finish on five under with 20-year-old Hall.
England's Florentyna Parker finished fifth on four under.
Munoz, who won her fourth Ladies European Tour title, lives 10 minutes from the Aloha Golf Club in Marbella.
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She said: "To be able to play here and just sleep at home, it's amazing.
"At the beginning of the week, I was so stressed out and so anxious and finally, when I got to the first tee on Thursday, I felt so much better.
"It is amazing to win in front of everybody and so many people came out, so I'm really grateful to them."
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England's Georgia Hall and Sophie Walker finished joint third as Azahara Munoz won the Andalucia Costa del Sol Open de Espana Femenino by a stroke.