Place cranberries, mandarin oranges, and pecans into a food processor and pulse several times to chop; process mixture until finely ground, about 30 seconds. Transfer mixture into a large bowl.
Mix pineapple, gelatin, sugar, boiling water, and cold water together in a separate bowl until gelatin and sugar have dissolved. Pour gelatin mixture into cranberry mixture and stir. Pour into a gelatin mold and refrigerate 8 hours or overnight before serving.
