There are many different fictional characters in the book series; From the Files of Madison Finn.

Madison Finn The protagonist of the series. Like her friends she is in seventh grade and attends Far Hills Junior High. Throughout the series, Madison writes about her daily life on her files which she uses as a personal diary. As well, Madison seems to be affected by the divorce of her parents from time to time in the series. The effect of the divorce results in Madison living with her mother and her pug Phineas T or rather known as "Phin". With everything going around her, Madison uses her orange laptop to write to her keypal "Bigwheels", go online and chat with her BFFS on BigFishBowl and write new files.

Ivy Daly The antagonist of the series. Ivy or "Poison Ivy" nicknamed by Madison and Aimee, is known as Madison's enemy. She is also refers as the "Queen Bee" and the Seventh grade president. Unlike Madison, Ivy is very popular and wants to be the center of attention; as she once noted that she is "revolving", but mistakenly said "revolsive". She was once best friends with Madison and Aimee when they were younger, as they used to play together in Ivy's treehouse all the time. Ivy is described as being beautiful by most of the seventh graders and "hot" by the guys. She is also very fashionable and modern as she tends to try and buy the latest/hottest activities and styles.

Aimee Gillespie  Is Madison's long time best friend. Aimee is a blond and thin girl who is pretty much a girly girl. She has been friends with Madison "ever since they were born". Aimee is very loyal to her friends and she can be extremely territoral when it comes down when Madison makes new friends. Aimee is described as being one of the prettiest girl in the seventh grade. She takes ballet very seriously as she trains before and after school.

Fiona Waters Is a new girl that moved to Far Hills (stated in the very first book in the series) and became fast friends with both Madison and Aimee. With her family and her twin brother Chet, Fiona moved to Far Hills from California. Fiona is usually a cheery person and yet, she is very gullible. Like Aimee, Fiona is very fit, as she has a talent for soccer and plays on the school team. She is the only one from her group of friends who calls "Egg" by his real name, Walter. Fiona is very opened as she tells Madison and Aimee that she has a crush on Egg in the second book.

Walter "Egg" Emilio Diaz Is Madison's old friend who is a boy. Egg and Madison knew each other since they were in kindergarden and it was noted that Egg had a crush on Madison. Later on, they described that their relationship was more as "brother" and "sister". Egg is known to be very obnoxious, loud, rude and annoying. He is also very intelligent when dealing with computers as he was the one to teach Madison the basics. Although his real name is Walter, he is referred as "Egg" because of a incident that happen when he was younger.

Drew Maxwell Is Egg's best friend and good friends with Madison. Drew's family is rich, he lives in a mansion and because of this, he often throws huge parties for an entire grade. Drew is described as "silly", but he is also the reasonable voice in the group of friends. He had a crush on Madison that was a bit too obvious and even asked Madison to the dance. He is very forgiving as he forgave Madison after she rejected him as a date to the "Heart to Heart" dance. Drew and Hart Jones are cousins.