Alice (Bonnie Hunt) and George (Charles Grodin) live in a big house on the outskirts of the city with their three children, Reith (Nicholle Tom), Ted (Christopher Castile) and Emily (Sarah Rose Karr), and live a peaceful and happy life until one day, a poor and lovely stray dog appears at the doorstep of Newtown's house. After the pleading of the three children, the puppy became a new member of the Newtown family and was named Beethoven. Time passed, and not only the three Newton children grew up, but also Beethoven. In just a few months, the originally petite and lovely Beethoven had become a giant creature, constantly causing trouble. Beethoven also brought deep happiness to the Newton family. Beethoven's existence attracts the attention of veterinarian Vanick (Dean Jones), and the evil doctor begins to do everything possible to keep Beethoven for himself.