If you’ve ever owned a Border Collie puppy, you likely know how fast they grow up. However, while growing up, its not immediately clear when your puppy becomes fully grown and is considered an adult. In this post, we will take a closer look when a Border Collie is officially considered fully grown.
When Is a Border Collie Considered Fully Grown?
While individual dogs may vary, most Border Collies reach their full height between 12 to 15 months of age. However, they may continue to fill out and gain muscle mass until they are around 18 months to 2 years old. Mental maturity often trails physical development, with some Border Collies not fully settling into their adult temperament until they are about 3 years old.
Factors Influencing Growth:
- Genetics: Lineage can play a significant role in determining the size and growth rate.
- Nutrition: A balanced diet rich in essential nutrients supports healthy development.
- Health: Parasites or illnesses can impede growth, making regular vet visits important.
- Exercise: Proper physical activity promotes muscle development and overall well-being.
Typical Border Collie Stages
Your Border Collie will go through a number of stages throughout their life. Here is a quick breakdown:
Growth Stage | Age Range | Physical Development | Behavioral Traits |
---|---|---|---|
Neonatal Stage | Birth to 2 Weeks |
|
|
Transitional Stage | 2 to 4 Weeks |
|
|
Socialization Stage | 4 to 12 Weeks |
|
|
Juvenile Stage | 3 to 6 Months |
|
|
Adolescence Stage | 6 to 18 Months |
|
|
Adult Stage | 18 Months to 7 Years |
|
|
Senior Stage | 7 Years and Older |
|
|
Frequently Asked Questions
What Factors Contribute to A Border Collie’s Growth Rate?
Do Male Border Collies Grow Faster Than Female Border Collies?

Donald Gregory is a devoted Border Collie enthusiast with years of hands-on experience raising and caring for this intelligent, energetic breed. Through practical advice and personal insights, he helps fellow owners nurture happy, healthy, and well-adjusted Border Collies.