Seldes, known for her role of Julia in play 'A Delicate Balance', died at her home on October 6.
The actress was a member of the drama faculty of The Juilliard School (1967- 1991) where Spacey was one of her students, reported New York Post.
Spacey, who was an aspiring actor then, recalls in the article, the moment he first met Seldes in the Big Apple with his friend Val Kilmer, and how she went on to change his life.
"She believed in her students. She believed in all her students. She revelled in their challenges, inspirations and aspirations, and her dedication to them was endless, it never stopped, not even after class was over, or if a student graduated or was even kicked out.
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Spacey added Meldes had an infectious smile and she was always there for her students.
Calling her a 'true teacher', the 55-year-old actor also said he was lucky to have the the Guinness Book of World Records holder as his mentor and credited his success to her guidance.
Other students of Meldes, who went on to become Hollywood stars were Christopher Reeve, and Robin Williams.