Integration of more communication standards in one microwave wireless device created a demand on developing compact, low-cost, and robust multi-band microwave components. This dissertation presents three studies for designing miniaturized and multi-band circuits that can be used for multi-band radio frequency (RF) front-ends. These three studies are the design of dual-band and tunable bandpass filters as well as dual- and triple-band equal-split power dividers/combiners. The dual-band filter is based on split ring resonators and double slit complemantary split ring resonators. A dual-band prototype three-stage Chebyshev filter, with a fractional bandwidth of 2% at 0.9 GHz and a fractional bandwidth of 3% at 1.3 GHz with equal-ripple of 0.4 dB at both passbands, is presented. The overall size of the dual-band filter is three times smaller compared to edge-coupled microstrip filters. Good out-of-band signal rejection (< 38 dB) and insertion losses (< 4.9 dB for the lower passband and <2.7 dB for the upper passband) are achieved. The proposed tunable filter is designed from varactor loaded split ring resonators. The size of the tunable filter is reduced by a factor of 3.5 compared to quarter wavelength-based coupled line filters.The power divider is based on composite right- and left-handed transmission lines. Dual-band and triple-band power divider prototypes are designed, fabricated, and tested. The passbands of the triple-band Wilkinson power divider are centered at 0.8 GHz, 1.3 GHz, and 1.85 GHz, and the passbands of the dual-band Wilkinson power divider are centered at 0.7 GHz, 1.5 GHz. The triple-band divider has a length of 0.66 wavelength in the substrate and its size is reduced to 3/4 of right-handed transmission line-based Wilkinson power dividers. The dual-band power divider has wide fractional bandwidths ( 20% at the lower passband and 41% at the upper passband). Excellent input matchings (input return losses < 29 dB), output matchings (output return losses < 23 dB), and output port isolations (< 24 dB) are achieved at all passbands of the power dividers. The proposed filters and power dividers are compact and low-cost, and are promising candidates for the miniaturization and cost-reduction of multi-band microwave wireless system.