Adobe buildings are located in many countries and are often constructed with fiber reinforced bricks, which are composite materials made of soil, water, and natural or artificial fibers. This study presents experimental findings for straw fiber reinforced adobe bricks typically used in Sardinia (Italy) and produced according to traditional worldwide handcrafted manufacturing procedures. A large number of compression and three-point bending tests were carried out on cubic and prismatic specimens, respectively. The identification of significant scatter in experimental data sets due to handcrafted manufacturing motivated the estimation of mechanical parameters at different percentile levels, in order to provide their characteristic and median values. The geometry of straw fibers was statistically characterized in terms of mean, standard deviation and probability distribution of their diameter and length. The mechanical characterization in compression included the estimation of fracture energy. Bending test data were processed to estimate Young’s modulus in tension, highlighting the bimodularity of the earthen composite material. Finally, both elastic–perfectly plastic and nonlinear stress–strain models are proposed for design/assessment purposes.