Peripherally active tetrapeptides as selective κ opioid receptor (KOR) agonists have been prepared in good overall yields and high purity following solid-phase peptide synthesis via Fmoc protection strategy. Structural modifications at the first and second position of the <i>lead compound</i> FF(d-Nle)R-NH<sub>2</sub> (<b>FE200041</b>) were contemplated with aromatic side chains containing d-amino acids, such as (d)-<i>p</i>F-Phe, (d)-<i>m</i>F-Phe, (d)-<i>o</i>F-Phe, which led to highly selective and efficacious KOR agonists endowed with strong antinociceptive activity <i>in vivo</i> following intravenous (i.v.) and subcutaneous (s.c.) administration in the tail flick and formalin tests. These results suggest potential clinical applications in the treatment of neuropathic and inflammatory pain.