There are 5 characters we meet in the story. They are Sue,  Johnsy, Behrman, a doctor and Mr. Pneumonia.

The main characters are Sue, Johnsy, Mr. Berman and they are the protagonist of the story as well. The secondary character is a doctor. Mr. Pneumonia is the antagonist. 

               

Sue’s image is created only by indirect characterizations. She is shown as a young girl and an artist who lives with her roommate and at the same time the best friend. 

She is very kind and good person. She is a caring individual, who waits and hopes for her friend’s recovery. Sue loves, always supports and encourages Johnsy. She is worrying about her heath condition. Also Sue doesn’t loses heart. After the doctor says the diagnosis and leaves she “cries a Japanese napkin to a pulp”, but then immediately cheers up and goes into Johnsy's room, “whistling ragtime” and proceeds to paint to earn some money.  We can understand from the context that she is a kind, hearty and merciful person.

       

                   

Another main character of the story is 

Johnsy.

She is a character developed through the indirect, speech characterization and interactions with others. She is ill. She is suffering from pneumonia.

At the beginning of the story Johnsy tends to be, in some extent, a pessimistic and weak person, because she gives up. The girl does not have a desire to fight off the weakness that her body has created after becoming ill.  She doesn’t want to fight for her place under the sun. She is the person who relies on fate. Her life depends on the last leaf. And only when she sees this last leaf remaining on the ivy, she begins to change. The girl mentally becomes a stronger person who receives a second chance to live. 

Mr. Bergman is another main character of this story. His image is created through direct and indirect characterizations. 

Mr. Behrman is an older man and lives downstairs the two girls. “Old Behrman was a painter who lived on the ground floor beneath them. He was past sixty and had a Michael Angelo's Moses beard curling down from the head of a satyr along with the body of an imp. Behrman was a failure in art…For the rest he was a fierce little old man, who scoffed terribly at softness in any one, and who regarded himself as especial mastiff-in-waiting to protect the two young artists in the studio above”; “…Behrman smelling strongly of juniper berries…”; “Old Behrman, with his red eyes plainly streaming”. These are examples of direct characterizations of the character. 

   Indirect characterization we can see through his lifestyle and actions. Although Behrman is down and out in art, he drinks wine to excess and he always mock terribly at softness of others, he is sympathetic and kind in nature. He  sacrifices his own life to help the poor girl. And this is the most precious. Though he was hard in the outside, he was full of gentle feelings in heart. 

Mr. Pneumonia is an antagonist of the story. In general, pneumonia is a disease in which the lungs begin to fill with fluid, making breathing harder. The author personified this disease in this story.  For example: «…a cold, unseen stranger, whom the doctors called Pneumonia, stalked about the colony, touching one here and there with his icy fingers. Over on the east side this ravager strode boldly, smiting his victims by scores, but his feet trod slowly through the maze of the narrow and moss-grown "places." Mr. Pneumonia was not what you would call a chivalric old gentleman. A mite of a little woman with blood thinned by California zephyrs was hardly fair game for the red-fisted, short-breathed old duffer». Pneumonia is portrayed as a character that battles and defeats many of the citizens.