Rinse the pearl barley under cold water. In a pot, combine with 3 cups of water and bring to a boil. Reduce heat, cover, and simmer for about 30 minutes until tender. Drain and let cool.

While the barley cooks, prepare the vegetables: dice the cucumber, halve the cherry tomatoes, and finely chop the red onion.

In a large bowl, combine the cooked barley (cooled), cucumber, cherry tomatoes, red onion, parsley, mint, lemon juice, olive oil, salt, and pepper. Mix well to combine.

Cover and refrigerate for at least 30 minutes before serving to allow flavors to meld.